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ISNDCM 2019

15th International Symposium on Nondestructive Characterization of Materials

Grand Hotel BernardinPortoroz

17 - 19 September 2019

ASNT and Slovenian Society for Nondestructive Testing jointly invite you to participate in ASNT's first international event, the 15th International Symposium on Nondestructive Characterization of Materials (ISNDCM), which will be held in beautiful Portorož, Slovenia at the Grand Hotel Bernardin.

The focus of the ISNDCM is the use of nondestructive evaluation methods as an investigation tool to determine the materials properties, and characterize parts of materials or features detected within them. This symposium will address issues of current and future interest, covering both theoretical and experimental work. Of considerable interest are the state-of-the-art developments and applications where the complex nature of materials is recognized. Presentations will also cover the applications and possibilities for multi-technique measurements of interdependent parameters and the evaluation of the data through sophisticated computer analyses.

We are facing a lot of numbers of infrastructures damaged seriously from the view point of fracture progress, so that assessment of damage for the deteriorated infrastructures is the first priority for establishment of life cycle scenario of those structures. Sensitive NDT to the tiny damages is not necessary for these structure with latter part of damage but NDT providing rough damage classification is sufficient to apply. A group of authors are thus studying tomographic approaches that coarsely quantify the interior damage with elastic wave parameters such as velocity, attenuation of energy and so forth. As for the former phase of damage, however, these techniques are sometimes insufficient to visualize the damage as it was so small scale and difficult to emerge with tomographic approaches using in-situ oriented sensors namely accelerometers. AE sensors directed to high frequency, detecting small damage are therefore employed for the early damage interpretation. In the presentation, state of the art technique for sensing the latter part as well as former part of damage in infrastructures are introduced. Specifically laser-induced elastic waves are used for the tomographic approaches for the latter damage and super wide band sensors covering Hz to MHz are applied and discussed using in-situ application.

CFRP are used in most wide domains due their low density, lack of mechanical fatigue phenomena and high strength –to weight ratio. Low strength to impact on the normal direction to fiber’s plane, leads to delamination and fiber breaking and these must be nondestructive evaluated in order to avoid further damage propagation. Also, the behavior of interlaminar fractures of composites is investigated numerically and experimental, the test being carried out with Arcan specimens that offer the possibility to use a single type of specimen in order to extract the fracture properties. The variation of loading between 0^0 and 90^0 allows the obtaining of different mixt modes. From electromagnetic point of view, CFRP structure represents an inhomogeneous structure of electric conductive fibers embedded into a dielectric material, thus an electromagnetic configurable architecture (CA) can be used to evaluate the materials.

Characterization of Commercially Available Infrared Cameras Using Photon Transfer Technique

Presenting author(s):
Mr Stefan Breitwieser

Co-Authors: Mr Gunther Mayr, Mr Gerald Zauner

Room: Adria | 9:15 AM Tuesday, September 17, 2019

Infrared cameras are an important component of the measuring and testing technology for contactless temperature measurement, e.g. in manufacturing processes or for nondestructive testing of various materials. However, the choice of a suitable infrared camera for a specific task, e.g. the thermographic inspection of composite materials, is usually a difficult and time-consuming task due to a variety of different infrared camera types available, which differ in the underlying detection principles, detector materials, acquisition speeds, spatial or thermal resolutions etc. Therefore, evaluation criteria that improve the comparability of infrared cameras would be advantageous.
The photon transfer technique (PT) is a well developed method for characterizing the performance parameters of optical camera systems, e.g. CCD (charge coupled device) and CMOS (complementary metal oxide semiconductor).
The aim of this work is the determination of the so-called ‘camera gain constants’ of commercially available quantum detector based infrared cameras using the PT technique.
Three different infrared cameras from various manufacturers are characterized by means of PT technique. In this way, the cameras are simply irradiated with a homogeneous radiation source (blackbody radiator) and the according signal and noise responses are recorded and displayed in a double logarithmic scale representation from which the camera gain constant can be deduced graphically. Exemplarily, the derived camera gain constants of two cameras (InSb detector and CMT detector) were determined to be 431 photons per digital number (DN) and 279 photons per DN respectively. Additional calculations based on Planck's radiation law were performed to verify the results.

Microwave Far Field Time Reversal Imaging in A Metallic Reflector Environment for High Resolution NDE Of Composites

Composites are being increasingly used in several industries to replace metals, fully or partially due to their unique properties such as high strength, durability and light-weight. The structural integrity of composites need to be evaluated for both manufacturing and in-service defects by a robust NDE system. Microwave NDE is particularly suited for interrogating composites due to their high sensitivity to low loss or lossless dielectric materials in comparison to other industrial NDE methods. Some of the recent applications of Microwave NDE involve detecting corrosion in painted steel substrates, disbond detection in carbon composites and Sprayed on Foam Insulation of space shuttles.
Although microwave far field imaging methods are non-contact in nature and particularly suited for rapid inspection at large stand-off distances the resolution of imaging is restricted by diffraction limits (of the order of the operating wavelength). On the other hand, while microwave near field imaging provides resolution much smaller than the wavelength, the scanning time is quite high, which is undesired for a rapid inspection system. This contribution focuses on improving the resolution of far field microwave imaging by utilizing the super-resolution properties of time reversal focusing in a metal-reflector environment.
Time reversal is a source focusing method which can be utilized to image defects that act as secondary sources in dielectric samples. The outgoing electromagnetic fields from the source not travelling towards the receiving antenna array are reflected by the metallic reflectors and directed back towards the array, leading to an increase in the imaging resolution. Numerical studies and experimental results are presented in order to demonstrate the capability and robustness of the approach for imaging disbonds in metal-composite joints.

3D Thermographic Reconstruction of Defects in Composite Materials

Presenting author(s):
Mr Gregor Thummerer

Co-Authors: Mr Gunther Mayr, Mr Peter Burgholzer

Room: Adria | 9:40 AM Tuesday, September 17, 2019

In this work three-dimensional (3D) thermographic defect reconstructions of composite materials based on the virtual wave concept (VWC) are presented. The intention of VWC-concept is to combine the two nondestructive evaluation methods thermography and ultrasonic testing. It has the following advantages: complex shaped components can be tested contactless using an infrared-camera for surface temperature data acquisition and ultrasonic reconstruction methods, such as the frequency domain focusing aperture technique (F-SAFT), can be employed for 3D thermographic imaging. The VWC is a two-step reconstruction method.
In the first step, the surface temperature signal of a thermally stimulated specimen is measured.
Based on this signal a so called virtual wave field is calculated. In the second step, inverse wave propagation methods such as F-SAFT are applied on the virtual wave field to calculate the initial temperature distribution. The transformation of the surface temperature field into a virtual wave field is an ill-posed inverse problem. Therefore, the iterative regularization method, called alternating direction method of multipliers (ADMM), is applied to compute an appropriate regularized solution and virtual wave field, respectively.
In the present work the performance of VWC considering a carbon fiber-reinforced plastic specimen with flat bottom holes is shown. Moreover, a three-dimensional defect reconstruction of a wood plastic composite material, obtained via VWC, is compared with the results obtained via computer tomography.

Experimental Comparison of the Emitter and Receiver Alternatives in Air-Coupled Ultrasonic testing of CFRP plates

Presenting author(s):
Mr Janez Rus

Co-Authors: Dr Balthasar Fischer, Mr Christian Grosse

Room: Mediterranean | 10:05 AM Tuesday, September 17, 2019

Piezoelectric-based transducers and receivers have currently a prominent role in the industrial contact-free inspection of CFRP (carbon fiber reinforced polymer) plates. However, there are innovative alternatives being investigated in the last years that have some explicit advantages. For the transducers, those advantages are broader frequency range, smaller excitation area and higher intensity of the emitted ultrasound (US). The sensors have an advantage in smaller acoustic aperture (and consequently better spatial resolution) along with the high sensitivity over a broader frequency range, comparing to the piezoelectric sensors. On the excitation side, we tested the nanosecond laser pulse, thermally inducing the ultrasound in the specimen, and compared it with another excitation alternative that is a focused thermos-acoustic transducer. On the receiver side, we used a laser-based membrane-free optical microphone adapting the Fabry-Pérot-Etalon principle. The measurements, made on the same specimens, allowed us to do a representative comparison.

Thermographic Testing of Abraded Silver Coated Teflon™ Tape

Silver coated Teflon™ (SCT) tape is a common thermal control coating for spacecraft but exhibits high specular reflectivity that can concentrate sunlight onto critical components. The specularity can be reduced by roughening the external Teflon™ surface via sanding processes. The optical properties (solar absorptance, emittance and specularity) of SCT tape test coupons that were uniformly abraded with 240 to 800 -grit sandpaper were measured and compared with typical mission criteria. A thermographic test was then devised to more directly assess the degree to which sunlight reflected from satellite components coated with abraded SCT tape would lead to a temperature rise of neighboring components. Here we report the results of the optical and thermographic testing that led to selection of a best candidate material for flight test. In a subsequent test, coupons of the unabraded and abraded SCT tape were installed onto the AeroCube 8 CubeSat to quantify the relative degradation in a low earth orbit environment. The observed solar absorptivity trends from the flight test will also be presented.

Adhesive bonded joints are more and more applied in modern structures. However, production defects and particular operative conditions may cause local de-bonding and catastrophic failures. Structural Health Monitoring and Non-destructive Testing procedures are, then, needed for evaluating the integrity of adhesive bonded joints during service.
In this research, an adhesive bonded single lap joint, whose both adherends are manufactured using a carbon fiber reinforced polymer composite, is subjected to a constant amplitude fatigue test. During such a test, the integrity and damage condition of the joint is continuously monitored by acoustic emission, while the test itself is periodically interrupted in order to carry out micro computed tomography of the specimen for investigating the real features of the damage.
Results show that monitoring by acoustic emission, after suitable elaboration and filtering my means of pattern recognition algorithms, allows identifying and charactering effectively the development of fatigue damage in adhesive bonded joints.

The provision of non-destructive testing of composite structures of unmanned aerial vehicles (UAV) suggests the possibility of creating flaw-resistant materials of a special new type. The specificity of UAV operation at high altitudes is the appearance of icing of its composite structures. To combat this phenomenon, electrothermal methods (ETM) are usually used, which put electric current for heating. In this anti-icing system, the directly operating unit is a special conductive layer containing heating elements and located between the insulating layers near the heated surface. The effectiveness of the anti-icing system depends on the presence of defects in the composite material and the working details.
Consequently, the task of using the integral approach of NDT to the Deicing/Anti-icing system of composite structures, which will allow combining anti-icing effect and quality control of the structure, is relevant.
The greatest effect on the anti-icing function in the case of UAV has a surface condition of the device. In this regard, we studied the influence of the surface of flaw detection materials, including for capillary control and improvement of their characteristics using magnetic indicators (the use of magnetic additives). So set, that the use of magnetic fluids in a constant magnetic field of a conductive system is an order of magnitude greater than the penetrating ability to detect surface defects by the capillary method.
Thus, in the course of the research, an integral approach to the diagnostics of the surface of composite structures and the improvement of the anti-icing system of unmanned aerial vehicles were proposed.

The increasing use of materials with complex internal structure, such as carbon fiber composites or recently introduced biocomposites, calls for versatile NDT methods that are suited to their specific properties. Traditionally, ultrasound NDT has a strong focus on liquid-coupled systems offering high acoustic bandwidth, and corresponding spatial resolution. Liquid contact, however, may be impractical or prohibited by the material properties – for instance moisture absorption in natural-fiber reinforced composites, or in the case of open-core honeycomb structures.
Such materials require non-contact testing offering high resolution and benefit from sufficient bandwidth for measurement of frequency-dependent attenuation or dispersion properties. Here, we demonstrate a setup comprised of fiber-coupled laser excitation and an optical microphone, which detects air-coupled ultrasound in a frequency range from 10 Hz up to 2 MHz. The microphone uses a laser to sense the small refractive index changes caused by acoustic waves in air within a 5 mm – sized capsule consisting of a miniaturized interferometer. The detection laser is not leaving the microphone - in contrast to vibrometric LUS detection, which often requires complex and bulky probe heads to handle varying surface roughness and reflectivity. In contrast, the optical microphone can be employed regardless of the surface properties. Compared to setups based on air-coupled piezoelectric transducers, the technology is apt for spectral measurements and offers notably higher spatial resolution.
Transmission-mode measurements on impact-damaged flax/PLA laminates, benchmarked against results from micro-CT and single-sided dispersion measurements on selected materials are discussed. The method was able to visualize defects with high resolution.

The study of magnetic materials properties is an important subject for different applications in fundamental and material science. For example, in steel, mechanical and magnetic properties are mutually related by material microstructure. The magnetic characterization of steel could allow non destructive testing of the mechanical properties during fabrication or in-service inspection. A number of magnetic methods have been studied.
Among the available techniques, magnetic imaging is a promising tool for steel characterisation thanks to its sensitivity to ferrite fraction. We have developed a 3D probe based on magnetoresistive sensors. Such sensors like Giant Magnetoresistive sensors (GMR) combine the advantages of a flat frequency response with a spatial resolution at the micron scale. The developed probe consists of four GMR sensors mounted on the sides of a square pyramid thus yielding four simultaneous field measurements along different directions
The advantage of this method is the possibility of simultaneous measurement of the three magnetic field components thus providing enhanced information about the magnetic properties of the specimen. After measurements, a reconstruction algorithm is applied to retrieve the three components of magnetic field from the four sensors signal. Another advantage of this technique is the possibility to measure magnetic susceptibility via superposition of an alternating magnetic field taking advantage of quantitative measurements of the magnetic field.
For the optimization of the measurement method and the better understanding of the field distribution in and above the considered specimen, a theoretical study has been carried out in parallel with the sensor development. The magnetic field is calculated by solving the magnetostatic problem taking into account the sensor geometry and assuming a known magnetization and susceptibility distribution in the material at the vicinity of the probe tip. For the solution of the magnetostatic problem, a hybrid numerical/analytical approach has been developed combining the finite integration technique (FIT) with an analytic propagator in the free space, which allows us to attain an increased accuracy at very small lift-offs.

Currently diverse advanced composite materials have been gotten widely application in many key industrial areas because of their unique mechanical, physical and chemical properties as light weight materials. The very practical industrial demand motivate us to develop new and advanced testing methods and techniques to see material structural details, evaluate discontinuities and defect in material body for finding better composite materials for interesting applications.
So far, there are different testing approaches for characterization and evaluation of composite method for different methods, including optical method, X-ray method, ultrasonic techniques for different testing samples in different macro-, meso- and micro-scale. The recent research results and industrial application practices have shown that ultrasonic imaging technique is very efficient and powerful testing method for observing material body structures, characterization and evaluating defects in many composites by using different ultrasonic approaches with different resolutions and systems.
One of the challenges is how to obtain useful structural details and different discontinuities, defects in large-scale sample and practical composite structures with sufficient high resolution. The main possible technical way is to increase ultrasonic frequency. But ultrasound in high frequency will bring a limitation of probing ultrasonic penetration in composite body, which will limit ultrasonic method to be applied in practical composite structures.
This presentation will introduce a new asymmetrical-frequency ultrasonic (AU) technique with rather high resolution for NDT&E of different composite materials and practical structures. Series of testing results and analysis about carbon fiber composites will be presented, including AU C-scan and B-scan. The resolution in depth can reach to the thickness of a single prepreg ply (approximately 0.125mm). The thickness to be tested can up to 50 mm by our new AU method.

Characterization of Structure of Steel Plates Using Acoustic Barkhausen Noise

Presenting author(s):
Mr Gabor Por

Co-Authors: Mr Janos Molnar, Mr Kristof Szikszai, Mr Peter Szabo

Room: Adria | 11:35 AM Tuesday, September 17, 2019

Applying low frequency external periodic magnetic field on magnetic materials, in our investigations on steel plates, one can observe the well know Barkhausen noise which is due realignment of the magnetic domains and it is traditionally detected by magnetic sensors. Recently it was observed that dislocations of magnetic domain walls during this process cause also acoustic emission, which can be detected by acoustic emission sensors. However, it is also known, that while magnetic Barkhausen effect is caused by 180omagnetic domain walls, the acoustic effects are due to perpendicular domain wall movement. Therefore there is a phase delay and also other deviations, which might depend on structure and stresses in the magnetic materials. In our experiments we use periodic sinusoidal magnetic field to produce both magnetic and acoustic Barkhausen effects. Since in both we have a nonlinear response, we get a two dimension picture on the graph showing the acoustic response in dependenve on magnetic answer, which have a characterizing form and parameters. Those parameters can give information on the structure of material. This measured form and its parameters can be compared with previously registered library data, thus distinguishing strength parameters of cold-rolled steel plates in parallel and perpendicular directions.

X-Ray Backscatter Technique for Inspection in Additive Manufacturing

Presenting author(s):
Dr Uwe Zscherpel

Co-Authors:

Room: Mediterranean | 1:00 PM Tuesday, September 17, 2019

X-ray back scatter imaging is rarely applied compared to classical X-ray projection imaging. More than 20 years ago the company Philips developed “COMSCAN”, a first application case for aircraft industry, which allowed even a depth resolution using back scatter imaging. The company AS&E in Boston offers back scatter imaging solutions for the security market. The principle is to scan the object with a highly collimated X-ray needle beam from one side only and to detect the backscattered radiation by a large area detector side by side with the collimation wheel. A new prototype is investigated at BAM for application and optimization in non-destructive testing. As modern industrial application field in-situ inspection in additive manufacturing is targeted. The accessibility of the printed part during the production process is very limited. This prevent the application of a two sided X-ray inspection or Computed Tomography, were an rotation of the object is required to acquire projections from 360 degrees. An important advantage for the X-ray back scatter technique are also the materials used in additive manufacturing (polymers, ceramics, light metals like Aluminum or Titanium). These materials with lower density and lower Z values give better scatter signals than metals with higher densities and Z values. The back scatter intensity decreases with increasing density and Z value of the material. But the requirements on spatial resolution and contrast sensitivity are more stringent for non-destructive testing of additive manufactured parts compared to the security area. In NDT sizes of indications smaller than 1 mm have to be detected clearly. The investigation of these limits on a state-of-the-art prototype for X-ray back scattering using rotating collimated X-ray needle beams is a part of the BAM project “ProMoAM”. The contribution shows first results of the optimization for NDT and the achieved application limits for several example cases.

Nondestructive defect characterization of pipelines allows companies to avoid costly repairs. Lamb ultrasonic waves generated through EMAT sensors have been recently used for this purpose allowing thickness estimation without direct contact with the surface of the metallic material. However, the behavior of the Lamb waves when they pass through the pipeline highly depends on the defect shape, and it is not easy to predict the residual thickness from the amplitude and phase of the waves. In recent studies the use of machine learning techniques applied to information extracted from signals sensed at different frequencies has been used to improve the accuracy of the estimation, demonstrating that the higher the number of frequencies used, the higher the accuracy of the estimations. On the other hand, it is also possible to analyze several modes extracted from a single frequency through multimodal analysis, using an intelligent selection of the frequency and the coil.
Thus, in this paper we study the relationship between the performance of the residual thickness estimation and the configuration of the sensing system. In this sense, a theoretical and experimental study of the selection of the coil and the frequencies for multimodal and multifrequency thickness estimation is tackled. First, a signal processing based theoretical framework is proposed. Then, the performance of the estimator using simulations obtained by a finite element software is analyzed. Results demonstrate the suitability of the methodology, improving the estimation of the residual thickness.

Open Configuration Portable X-Ray Computed Tomography

Presenting author(s):
Dr Joseph T Case

Co-Authors: Dr Shant Kenderian, Dr Eric C Johnson

Room: Mediterranean | 1:25 PM Tuesday, September 17, 2019

X-ray computed tomography (CT) is the standard for volumetric inspection. However, it suffers from the limitation that the part or specimen under inspection is typically placed into a stationary cabinet or ring for which the x-ray source and detector are rotated. Thousands of x-ray shots are acquired at unique angles of incidence, which are subsequently processed to reconstruct a volume image of the specimen. The volume is then rendered or sliced for analysis. Obviously, not all parts are conducive to be placed in a cabinet or ring. Furthermore, it may be desired to inspect only a small region of interest on large parts. For such parts encountered in the field, only a limited number of unique angles of incidence are reasonable or possible when acquiring x-ray shots. Improved x-ray shot acquisition and reconstruction processes are desired to be able to reconstruct volume images from limited shots. Such a system may be lightweight and flexible in order to support an open configuration where arbitrary positioning of the x-ray source and detector are possible. Unfortunately, such an acquisition system may encounter positional and orientation inaccuracy. Therefore, the reconstruction process should also take these into account. Lastly, the reconstruction process should be available in the field; that is, computation resources must be small and lightweight. Thus, it is required that the system exploit small and lightweight high performance computing (HPC) resources like graphics processing units (GPUs) or co-processors. This work describes preliminary results into a prototype system that attempts to solve the above-mentioned problems: limited shots, lightweight x-ray source and detector positioning, and efficient use of small-footprint computational hardware.

It is now generally recognized that acoustic emission (AE) technology is extremely the best tool to determine the flaws from material structures as a non-destructive method. Over the years, the AE test method has been studied for the monitoring and inspection of defects related to gas leaks from pipeline facilities. Its application is considered as an efficient and cost-effective process among other relevant methods. It is known that in the case of artificial defects being pinholes, there is a possibility of position location [1]. In this paper, the AE characteristics detected during gas leak from the pipe with artificial defects of slit are examined and the source location of the leak parts is to be revealed.
The steel pipe (JIS SGP 20 A for general piping) has an outside diameter of 27.2 mm and an inside diameter of 21.8 mm, and the corresponding length is 1500, 2500 mm. The AE sensor (M5W, Fuji Ceramic) was attached to the test piece and measured. The signal from the AE sensor was amplified to 40 dB. The AE parameter used is the average amplitude and the peak frequency for each waveform constituting the continuous AE. A graph was created based on these and the pressure when AE occurred.
Even with slit-shaped artificial defects, the peak frequency showed the screech tone observed during the jet collision flow. The first decreasing curve is an asymmetric mode, and the second decay curve is a symmetric mode. The third one is shown as the reflecting waves due to the asymmetric mode. By using the pressure at a certain peak frequency, it was possible to obtain the limit distance of the artificial defect and the AE sensor. As with pinhole, increase and decrease of average amplitude could be observed. This increase and decrease can be considered as resonance with noise due to decrease in peak frequency.
Differences occurred in experimental results depending on the pressure. Therefore, it did not reach position locating. However, it was found that the limit distance between AE sensor and artificial defect is about 2400mm.

We are presenting our last technical achievements in the field of industrial fast X-ray imaging techniques for high-resolution in-line quality control. First we are describing our X-ray high-resolution digital radiography scanning machines based on mini/microfocus X-ray generators and X-TDI (Time Delayed Integration) and/or Flat Panel detectors and their main applications. Then, we are introduction our most recently designed and manufactured system: a complex in-line belt-based scanner for fast internal integrity and critical dimensions control of ballistic sintered plates manufactured by Nurol company from Turkey. Within new equipment have been combined two advanced techniques: the laser based profilers for getting the full 3D plates’ shape dimensional measurement, including thickness, followed by an X-ray digital imaging set-up for plates’ internal defects detection based on a minifocus X-rays source and two X-ray TDI detectors. The new belt–based system is scanning the sintered plates with the laser profilers, determining if sample’s 3D shape and overall dimensions are within the acceptable dimensions, followed by the internal defects detection by a high-resolution X-ray digital transmission imaging system. The system is able to scan with both techniques a sample with typical size of 240x290 mm2 in a bit more than one minute time, that include the sample load and upload time. The laser profiler is able to measure sintered parts having maximum size of 300x400 mm2 with overall dimensional relative accuracy measurement of less than 2% and the achievable X-ray images resolution is around 70 microns, enough for detecting the thinnest possible defects, including cracks. In the final part we present various sintered and green samples measurements scanned taken with our various equipment, containing a large pallet of defects, such as cracks, inclusions, pores and density variations.

Acoustic Assessment of The Internal Stress and Mechanical Properties of Gas Pipelines

Presenting author(s):
Mr Lyudmila Volkova

Co-Authors:

Room: Adria | 1:50 PM Tuesday, September 17, 2019

The failure of many metallic structures, including gas pipelines, is most often due to high residual stress, which may reach the yield point, especially in the region of stress-corrosion cracking (SCC). That leads to a stress concentration, accelerating defect development and markedly curtailing the working life. The most promising is ultrasonic monitoring based on acoustic elasticity. The waves are emitted normally to the gas pipelines’s contact surface. The pulses are recorded by a specially developed SEMA electromagnetic–acoustic structurescope.

The measurements of an acoustic method are made by means of an electromagnetic–acoustic converter on the basis of the measured difference in the time for two orthogonally polarized shear waves to pass from the one side to the base of the gas pipelines and back.

The SEMA instrument includes an electric-pulse generator, which forms a powerful electric probing pulse. The electromagnetic–acoustic converter excites and receives short acoustic transverse-wave-pulses.Other components include an amplifier and an analog–digital converter built into the computer.

The software compares the pulses of two incoming signals; and measures their amplitude and the difference in the times at which the signal passes through zero. Since the program employs coherent time accumulation and autocorrelation analysis, it is possible to ensure an instrumental error of ±2N/mm2 in assessing the voltage.

Gas pipelines samples from different surface condition are tested. The relation of the residual stress to the hardness characteristics of gas pipelines steel is investigated. The speed of the bow waves and surface waves correlates well with the stress measured by tensometric converters (correlation coefficient 0.96). From test results for elements of full-scale gas pipelines, the range of longitudinal residual stress measured by the SEMA instrument in the gas pipelines is 20–50 N/mm2.

According to the area of the three samples, the distribution of the stress state both in the axial direction s1 and in the circumferential direction s2 is very uneven and differs for samples with a welded seam and in the presence of SCC. The presence of corrosion cracking in samples No. 1 and No. 3 led to a significant change in the distribution of the stress state. Sample No. 1, partially (to the right) cleaned up from SCC, led to a decrease in stresses in this area, in contrast to the SCC area, where the stresses are much higher. Note that axial stresses in areas of SCC with orientation of cracks along the envelope are significantly higher than circumferential ones, which is explained by the concentration of axial tensile stresses with SCC cracks. Sample No. 3 has a significant corrosion cracking over the entire area, which has led to an extremely uneven distribution of the stress state around the circumference of the pipe, while the stress state along the pipe generator does not undergo significant changes.

This work was supported by the Russian Science Foundation (project no. 18-79-10122).

Evaluation of SiC/SiCf Composites by Multiple Imaging Techniques

Presenting author(s):
Mrs Feifei Liu

Co-Authors:

Room: Mediterranean | 2:15 PM Tuesday, September 17, 2019

Currently SiC/SiCf composite materials have been gotten important applications in manufacturing a couple of aero-engine parts because of their excellent mechanical properties in high temperature condition as light weight materials. So, a lot of research and development attentions have been paid to SiC/SiCf Composites in recently years. One of them is the characterization and evaluation of defects in SiC/SiCf composites because of their very unique materials preparation and forming technology process by CVI, PIP or PMI method. Internal inhomogeneity and defects, such as porosity, voids, delamination, etc., may be induced during their manufacturing. It is much difficult to evaluate and detect out all these possible manufacturing-induced defects in SiC/SiCf composites by using conventional nondestructive testing techniques or methods because of complexity of SiC/SiCf composite internal microstructures and diversity of defects. For example, a SiC/SiCf composite with high porosity content will become to be undetectable when a normal ultrasonic testing (UT) technique is employed. In this speech, we will present a multiple imaging technique, in which a new ultrasonic imaging and digital X-ray (DR) scanning imaging techniques were used for characterization and evaluation of defects in SiC/SiCf composites. A series of SiC/SiCf composite samples, which were manufactured by PIP technology process, have been manufactured. Multiple ultrasonic imaging techniques with different frequencies and probe beams have used to investigate the detectability of defects in the samples. After UT evaluation, a DR scanning imaging testing by using micro-focal spot X-ray beam has been performed to each sample as a comparison with UT result. The experimental results showed that the porosity with different contents, delamination and voids in the specimens can be found out by our employed UT imaging techniques. The cracks and inhomogeneity in the specimens can be characterized and evaluated by DR scanning imaging technique. The combination of the UT and DR techniques can give a very good characterization and evaluation of defects in SiC/SiCf composite.

As for marine and ship engineering, seawater pipelines are widely used as cooling, fire water and rinsing system. Since seawater is so corrosive media for metals, especially under high velocity seawater moving condition, copper alloys have taken over the dominance of pipeline materials for anti-corrosion and anti-fouling. However, the pipeline metals suffered severe corrosion after a couple of years in service, which might cause serious corrosion failure, leakage and other accidents. Therefore, in situ corrosion inspection by nondestructive technology (NDT) for those pipelines is highly demanded. In this paper, digital X-ray technology was introduced into the corrosion inspection of seawater pipelines. A set of portable device including control software was developed and applied to seawater pipelines in field. Some typical digital radiography images were taken and the residue thickness of the pipes was calculated by the software and further analysis. Thus, the corrosion degree and the future service life of the seawater pipelines could be evaluated by such kind of technology successfully.

The String Model A New Interpretation Of The Metallic Structure And Its Connected Physical Phenomena

Presenting author(s):
Dr Giuseppe Nardoni

Co-Authors:

Room: Mediterranean | 2:55 PM Tuesday, September 17, 2019

String theory has been for a long time a keyword in the advanced physics texts. Stephen Hawking, just in recent years recommend to his students to study string theory. The paper analyses the principles of the theory forgetting its complex mathematical presentation and visualize how the string model may explain the behavior of the metallic structure under different conditions of stress, magnetic field, hardening process, strengthening, etc… Recently in an article of prof Subir Sachdev published on Scientific America Magazine 1 explains through a quantic point of view that string theory and string model may be applied also to solid material. With simple example the paper highlight how in the case of steel structure same characteristic behavior, as the strengthening of steel may be easily explained by the string theory or string model as the ACADEMIA NDT INTERNATIONAL defined and approved during a meeting in Brescia

On the Use of Acoustic Emission for Detecting Quenching Bath Property Deviations

Presenting author(s):
Mr Bor Mojskerc

Co-Authors: Dr Janez Grum, Mr Tomaz Kek

Room: Adria | 2:55 PM Tuesday, September 17, 2019

This research paper describes the use of non-destructive, acoustic emission (AE) testing for monitoring the quenching bath property deviations. Steel quenching is a common heat treatment process, used to improve the mechanical properties of different workpieces. The cooling characteristics of quenching baths change with excessive use and ageing and in turn influence the mechanical properties. A preferably non-destructive method of bath evaluation is therefore required. In this paper, an AE measurement system is proposed and a proof of concept quenching evaluation method is developed. Cylindrical steel specimens are quenched in baths, such as tap water, deionized water, 5 % salt-water solution or 5 % detergent-water solution. The AE is detected with several passive resonant piezoelectric sensors, which are commonly used in the field of non-destructive AE testing. The influence of quenching bath property deviations on cooling characteristics is described in correlation with the measured AE signals. AE signal peak amplitude over time diagrams are examined. A referential AE peak amplitude signal is established in correlation with the measurements. The quenching bath property evaluation method is based on monitoring the number of outlying AE signal packets in comparison with the referential AE peak amplitude signal. The experimental results confirm that the described method is a reasonable way of evaluating the property deviations of liquid quenchants and in turn their influence on workpiece mechanical properties after quenching.

Prediction of the Visibility of Indications in X-Ray Computed Tomography by the Contrast Detail Diagram

Presenting author(s):
Mr Uwe Ewert

Co-Authors:

Room: Mediterranean | 3:20 PM Tuesday, September 17, 2019

X-Ray Computed Tomography (CT) is applied in industry for flaw detection, flaw evaluation and dimensional measurement. This requires the correct CT system settings for sufficient visibility and detectability of flaws and structure elements. The visibility of indications for human observers on a monitor depends on the square root of the reconstructed flaw area (here pores with diameter < ½ inch) in the cross sectional 2D images, the Contrast to Noise Ratio (CNR) and the Modulation Transfer Function (MTF). This applies also to 2D-projections, meaning also to “normal” digital radiographs. The ASTM guide E 1441 describes three essential functions for prediction of the visibility of small circular indications in slice images of a 3D reconstruction or a 2D reconstruction. This is the Contrast Discrimination Function (CDF), the MTF (see also the revision of ASTM E 1695), and the Contrast Detail Dose (CDD) function. The prediction of the visibility of circular indications in reconstructed slice images can be determined from the Contrast Detail Dose function, which is the combination of CDF and MTF and a physiological factor c. The measurement procedures and formulas for the prediction of the detail visibility by CDD will be corrected, tested and verified by modelling and in a Round Robin Test with modern commercial 3D CT systems of different manufacturers. Conclusions will be reported and recommendations will be given for the correct psychological factor c and the consideration of the influence of artefacts, as e.g. cupping and scatter.

Investigation of The Failure of Oxide Coatings on Aluminum Alloy Using the Method of Acoustic Emission

Microarc oxidation (MAO) is the surface treatment processing for metals and alloys of a valve group, which consists in the fact that the surface of oxides in the electrolyte is exposed to high-amplitude electrical pulses. The resulting oxide has characteristics of high density and adhesion. Materials with MAO coatings have high wear resistance, corrosion resistance and electrical insulation of the product. Various microarc oxidation technologies influence the characteristics of the resulting coating. When using the method of acoustic emission during testing of products with coatings, it is necessary to take into account the features, which are associated with recording signals from the coating and distinguish them from signals recorded during structural changes in the substrate material. This article presents the results of the study of samples with an oxide coating applied by an MAO method on an aluminum alloy, during mechanical testing of tensile samples while simultaneously recording acoustic emission signals (AE). The samples were coated with various thicknesses by changing the oxidation time. The paper presents the results of a study of the effect of the thickness and density of oxide coatings on acoustic emission signals at various stages of static tension of samples. After mechanical testing and failure, the samples were made surface grinding and polished to determine the nature of the failure of the coatings and the interphase region. The results of the experiment show that the thickness of the microarc oxidizing coating has no significant effect on the tensile strength and elongation at break of the aluminum alloy. However, based on the analysis of parameters such as the accumulation of acoustic emission signals, amplitude, energy and median frequency, those were revealed the totality of the acoustic emission parameters and their numerical values, which were characterizing the destruction of the oxide coating and substrate. The regularities of changes in the recorded parameters of acoustic emission, which were obtained as a result of experimental studies, can be used to describe the various stages of deformation and tension of aluminum alloys with oxide coatings applied by the MAO method.

Nonlinear acoustics and vibration has become increasingly important during the last forty years due to the increase of higher sensitivity of electronic instrumentation and its associate signal processing algorithms. The nonlinearity of materials results in nonlinear effects, which arise from defects in the materials present at all scales [1]. Applications include nonlinear nondestructive testing (NDT), harmonic medical ultrasound imaging and development of new materials such as nanocomposite and memory based materials [2]. One of the strategic plan of the international NDT community is to define standards for developing nonlinear non-destructive testing for automated set-up in mass production [3].
The aim of this paper is to present round robin tests performed in an aluminum sample presenting a calibrated slit and a hole with the same size. The paper presents the Time Reversal based Nonlinear Elastic Wave Spectroscopy TR-NEWS device which is associated to the development of a phenomenological characterization of material local elastic properties [1] working at 20 MHz allowing the measurements of degradation and aging of complex structures. The experimental device was tested with the V3 calibration block, improved and specially scaled in order to access to a wide range of multivalued parameters: mechanical properties, ultrasonic parameters (celerity and attenuation) and local geometric data. Also tested for biomedical applications too, the well-known complexity of the sample constitutes a strong advantage for the TR-NEWS efficiency. Linear and nonlinear signatures of material properties are measured locally thanks to an optimized signal processing involving time reversal, correlation and pulse inversion algorithms.
[1] B.E. Anderson, M.C. Remillieux, P.Y. Le~Bas, T. Ulrich, Nonlinear Ultrasonic and Vibro-Acoustical Techniques for Nondestructive Evaluation, Springer, 2019, pp. 547--581
[2]D. Burgos, L. Mujica, J. Rodellar, Emerging Design Solutions in Structural Health Monitoring Systems, Advances in Civil and Industrial Engineering Series (IGI Global, 2015)
[3] Serge Dos Santos, Martin Lints, Denis Arruga, Ali Masood and Andrus Salupere, Standards for acousto-mechanical evaluation of multiscale hysteretic properties of complex material with nonlinear time reversal imaging https://www.ndt.net/article/ndt-slovenia2017/papers/49.pdf , in proc of the ICNDT 2017, Portoroz.

Checking the Homogeneity of Metal Plates Using Scanning Nondestructive Methods

Presenting author(s):
Mr Gabor Por

Co-Authors: Mr Janos Molnar, Mr Peter Szabo, Mr Szebasztian Szabo

Room: Adria | 3:45 PM Tuesday, September 17, 2019

Scanning nondestructive testing is a rapidly developing area, which connect the precise mechatronics motion with the nondestructive testing sensors. The automatic small step repetition of the measured signals with steps of 0.1 mm opens the way to compare the measured values in each step. Thus if there is a material degradation or non-homogeneity or any other flaw in the material the difference detected in consecutive steps can be used for their detection. Our method includes a program driven step motor motion. The excitation is made by magnet. The reception side is an acoustic emission sensor and magnetic sensors. We present our results in developing such method that opens the way to detect any non-homogeneity in metallic plates.

Industry 4.0 is named after three industrial revolutions: mechanized industrial processes, assembly lines and robotic systems. Industry 4.0 comprehends complete networking within industrial processes, raw materials, design with consideration to non-destructive testing, production and more or less central quality control.
Industry 4.0 is the relevant project in Germany implemented and promoted by state institutions. With available networking possibilities, it will in addition be an important future aspect in industrial processes. It is believed, that nearly all areas involved in the industrial process are affected.
The question arises as to which extent it will influence the area and profession of NDT as a technique and related human resources. What would be the requirements of NDT4.0?
The German Society for Non-Destructive Inspection (DGZfP) has taken the requirement and founded corresponding Technical Committees.
Some aspects of the integration of the inspection results and quality control and online information to the production department are not new for NDT.
In this paper, an attempt is made to analyse strengths, weaknesses, opportunities and threats (SWOT) within the area of NDT.
The overall networking of NDT4.0 includes all aspects within the industrial process. It requires comprehensive automation in the NDT test procedures and available information. Intelligent sensors which are deciding IO or NIO, providing online statistics to the quality and back to the process department obviously will be additional demands to the NDT testing procedure.
During this presentation, a completely automated system for magnetic particle inspection of steering knuckles, and other components are described as examples.
The systems consists of robotic placement of the part for applying the magnetic powder to the areas of interest, to camera and lightning components. Automated evaluation of the defect indications by the computer using image-processing techniques involving different algorithms. The computer is connected to the manipulation system and deciding IO or NIO according to the quality requirements. Additionally the computer calculates relevant statistical information. Networking with all interested parties in the production process can be provided.

Registration of Acoustic Emission Waves in An Isotropic Plate Using Fiber-Optic and Piezoelectric Sensors

Acoustic emission (AE) is a method of diagnostics based on the registration of acoustic waves, which are propagation due to the actions of stress in the material. To register these acoustic waves, it is necessary to develop sensitivity of sensors that are easy to attach and protect electromagnetic interference. One of solving of these challenges in the directions of systems for monitoring the stress-strain state of objects is the use of fiber-optic sensors. The achievement of high sensitivity of these sensors, stability and to prevent noise immunity became possible with the use of adaptive laser interferometers. Therefore, in this work the construction of fiber-optic sensors is based on the two-wave interaction of laser radiation with a dynamic hologram formed in a photorefractive crystal. For investigation propagated AE waves in the isotropic plate the AE source is generated by the pencil-lead breaks (Hsu-Nielsen source) on the surface of the specimen. AE signals are registered the same time by fiber-optic and piezoelectric sensors, which are located at the different places of plate. The difference of sensitivities of sensor allows to detection of AE signals in different frequency band. Wavelet transform was used to isolate a useful signal from noise and to investigate limitation of sensitivities of the propagating waves of both sensors. As a result of the analysis of acoustic emission signals, the spectrum of fiber-optic signals is associated not only with the peculiarities of wave propagation in the plates, but also with the size of the plate and the length of the fiber-optic sensor.

Acoustic Emission During Compression Tests of Ti-Mo-Si Alloys Used for Medical Prostheses

Presenting author(s):
Mr Zdenek Prevorovsky

Co-Authors:

Room: Mediterranean | 4:35 PM Tuesday, September 17, 2019

Titanium
and its alloys are due their unique properties used as materials for medical
prostheses and other devices. Titanium properties as low density, high
strength, stiffness, and fracture toughness, along with corrosion resistance
and biocompatibility, may be further enhanced by combining with other alloying
elements like e.g. Mo, Si, Zr, V, etc. Especially ternary alloys Ti-Mo-Si have
gained the attention of biomedical industry due to their specific
bio-functional characteristics properties and the best biocompatibility among
metallic materials used in medical implants and prostheses. Alloying Ti with Mo
(10-20%) stabilizes b-Ti phase with small grains, and adding of 0 to 1.5 %
of Si can further enhance compressive and yield strength, and decrease porosity.
In order to characterize the influence of chemical composition on the structure
and mechanical properties of Ti-Mo-Si alloys, the determination of elastic constants
matrix, mechanical resistance and the probability of appearance and propagation
of cracking were experimentally studied. The resonant ultrasonic spectroscopy
(RUS) and acoustic emission (AE) as nondestructive evaluation methods, along
with complementary methods SEM, and EDX were used to compare properties of four
Ti+15% Mo alloys with different concentrations of Si elements (0, 0.5, 0.75,
and 1 %). Small cubes (10 mm side) were tested in compression below the
strength with continuous registration of AE signals, and various AE parameters
were then evaluated. The results show that samples of alloys with higher Si
concentration have lower AE activity due to cracking, which may be used to
optimize alloy composition for medical prostheses.Titanium
and its alloys are due their unique properties used as materials for medical
prostheses and other devices. Titanium properties as low density, high
strength, stiffness, and fracture toughness, along with corrosion resistance
and biocompatibility, may be further enhanced by combining with other alloying
elements like e.g. Mo, Si, Zr, V, etc. Especially ternary alloys Ti-Mo-Si have
gained the attention of biomedical industry due to their specific
bio-functional characteristics properties and the best biocompatibility among
metallic materials used in medical implants and prostheses. Alloying Ti with Mo
(10-20%) stabilizes b-Ti phase with small grains, and adding of 0 to 1.5 %
of Si can further enhance compressive and yield strength, and decrease porosity.
In order to characterize the influence of chemical composition on the structure
and mechanical properties of Ti-Mo-Si alloys, the determination of elastic constants
matrix, mechanical resistance and the probability of appearance and propagation
of cracking were experimentally studied. The resonant ultrasonic spectroscopy
(RUS) and acoustic emission (AE) as nondestructive evaluation methods, along
with complementary methods SEM, and EDX were used to compare properties of four
Ti+15% Mo alloys with different concentrations of Si elements (0, 0.5, 0.75,
and 1 %). Small cubes (10 mm side) were tested in compression below the
strength with continuous registration of AE signals, and various AE parameters
were then evaluated. The results show that samples of alloys with higher Si
concentration have lower AE activity due to cracking, which may be used to
optimize alloy composition for medical prostheses.

Computational power of contemporary standard hardware enables to test the new approaches in many fields. In case of non-destructive evaluation and material characterization by Acoustic Emission (AE) method it is possible to monitor highly dynamic damage processes as could not be done before without the capability of continuous signal recording and analysis. Modern portable measuring devices as USB oscilloscopes with data streaming feature can be flexibly controlled by scripts tailored for particular experiment. AE activity can be thereby evaluated on-line in more details by specially designed parameters. The running experiment can be controlled by actual state of material damage as well. Such approach is demonstrated during the test of titanium alloys for medical implants. The AE method provided comprehensive data to identify the initial stages of damage and crack propagation in the stressed specimen. AE measuring and evaluating system based on USB oscilloscope TiePie was completely designed and run in Matlab environment. Display of basic AE parameters, audible monitoring of selected AE hits and saving all those parameters together with the complete signal stream in binary format for further advanced analysis, was possible in real time.

Dr Roman Gr Maev

The Innovative Solutions for Non-Invasive Evaluation of the Fine Art and the Cultural Heritage Objects and for Forgery Detection via Unique Patterns Matching

Presenting author(s):
Dr Roman Gr Maev

Co-Authors:

Room: Mediterranean | 8:15 AM Wednesday, September 18, 2019

Industries can save tons of time and money if it makes nondestructive inspection less error-prone. For those reasons, R&D in this direction began to be one of the top priority and recent development in this field demonstrate really promising results.

In this presentation, we will discuss a few most promising concepts which currently are under strong development by a few international research groups. We will present some successful results in this field and one of them is Real-time automated spot weld quality analysis from ultrasonic B-scan using deep learning. This is the first work in this direction where was applied deep learning based framework for in-line detection of objects of weld shape from ultrasonic b-scans. Applying deep learning interpret detected components to numeric features and classify welds as good, acceptable or bad in real-time during production. This solution allowing NDE specialists to improve the existing automated system to produce high weld quality classification accuracy that matches with production-level satisfaction.

A Damage Science Based Monitoring Approach for Detecting End-of-Functional Service Life

Presenting author(s):
Dr John C Duke, Jr

Co-Authors:

Room: Mediterranean | 9:15 AM Wednesday, September 18, 2019

Engineering materials including fiber reinforced polymeric composite materials as well as metal alloys develop damage during service when used in structures where structural integrity is critical. This damage development will occur throughout the structure depending on the applied load level more or less from the time the service begins. In regions where no geometric detail causes stress concentration the occurrence will be globally distributed, while in some regions where geometric details cause stress concentrations a localization progression will proceed early in the life. Where globally distributed damage develops initially it will eventually become localized and typically when this localization of further progressive damage occurs the rate of development begins to rapidly increase. Typically, health monitoring R&D has focused on novel sensors or wireless devices, or energy harvesting with little actual attention to application to monitoring health. Here an approach which is directed at detecting the transition of damage development to localized development, or the significant increase of precursor damage development in regions where damage development is forced by geometric details to be localize initially will be described and experimental results presented.

The Non-Destructive Method of Elasticity Modulus Measurement of Valve Seats from STELLITE with Various Cryogenic Stavs

Presenting author(s):
Mr Bretislav Skrbek

Co-Authors:

Room: Adria | 9:15 AM Wednesday, September 18, 2019

Function and straining of piston combustion engine valve seats. Utrasound diagnostics of composite valve seats (steel-graphite) durability. Pilot experiment in region of cryogennic temperature influence on mechanical properties of cobalt hot wear resistant alloys of STELLITE group determination. Cobalt alloys are exploited due their excellent mechanical properties at high temperatures as a matter for valve seats of gas combustion engines. From the technological view the valve seats are frozen in liquid nitrogen before assembling because of big assembling overlaps which should assure reliable anchoring of valve seats in heads of cylinders. The anchoring force depends on elasticity modulus of valve seat and head of cylinders. The non-destructive method of elasticity modulus measurement in the region of bore for valve seats placing of composite cylinder heads. In the case of undercritical value there is a danger of falling out of seat from cylinders head under influence of thermal expansivity of head alone. The measurement of sound speed and magnetic properties of valve seats from STELLITE 6 and STELLITE 12 with various cryogennic stays. The expressive minimum of sound speed at critical cryogennic stay. The link proof of sound speed minimum and elasticity modulus by non-destructive measurement of valve seat ring bent at hardnessmeter loading. The mathematical pattern of calculation. This contribution serves to finding if this manufacturing technology of valve heads has an effect on useful properties of valve seats – direction of next research.

The monitoring of the steel components during long term in-service life under the influence of the operational factors is important as part of the components maintenance. The local coercive force measurement technique using with surface type probes can create effective background to solve this task. There are known many investigations and successful practices concerned with of the coercimetric method application. In presented paper the main principles of the coercimetric method and tools are presented. Investigations concerned with two novel applications are presented also.
First investigations were related to the steam pipelines of power plants operated under high pressure (up to 16 MPa) and elevated temperatures (up to 570º C). As a result of long-term operation the initial structural and phase state of materials are transformed. These factors lead to changes in the mechanical characteristics of materials. It is especially important for the areas of pipelines with high level of stress and strain concentration. The objective of this study is to establish the regularities of coercive force changes for 12Kh1MF and 15Kh1M1F steels of the steam pipelines bends after long-term operation (175–280·103h) depending on the phase composition and microdefects needed for development of the new methodology for prediction of the steam pipelines residual life. The possibility to evaluate the structural-mechanical states of the steels of steam pipelines after long-term operation by measuring their coercive force is shown. The ultimate values of the coercive force of investigated steels, possible to be applied for prediction of the critical state of steam pipelines, were determined.
Second investigations were concerned with the estimation of stresses by the measurements of the coercive force distribution along ship load-bearing elements material during operational loading. The measurements were done on the hatch coamings of the “river-sea” cargo ship. It was shown that areas of highest coercive force (and mechanical stresses) are not in compliance with the recommendations of the International Maritime Organization concerned the strain gauge placement. New strategy for ship construction monitoring based on the coercive force measurements in the preliminary determined critical zones was proposed.

Identification of a Crack Using Frequency-Dependent Directivity of Ultrasonic Waves

Presenting author(s):
Mr Kazuki Mura

Co-Authors: Dr Toshihiko Sugiura

Room: Adria | 9:40 AM Wednesday, September 18, 2019

Generally, ultrasonic testing for open cracks estimates the position and size of cracks from propagation time and amplitude. However, piezoelectric probes have a problem that the amplitude varies depending on inspector’s skill. On the other hand, in our previous research, we confirmed that low-frequency components were included in the ultrasonic waves which propagated in the oblique direction and that there is a relation between the ratio of low-frequency components and the directivity of the waves. This relation can be potentially used as a flaw detection method independent of the amplitude. Thus, we propose a new ultrasonic testing method using two different frequency components which have different directivities. This method may not depend on the installation condition of ultrasonic transducers.
We first experimentally confirmed that the received angle of the ultrasonic wave can be estimated by comparing the amplitudes of the two received waves which differ in frequency. In next experiment, we used two kinds of specimens: one with a slit perpendicular to its upper surface, and the other with a slit parallel to its upper surface. These slits, imitating cracks, were created by wire electric discharge machining. We experimentally demonstrated that the position of the slit tips can be estimated on the basis of the confirmation obtained from the first experiment above. These results show that the crack tip position can be successfully identified by the proposed method using two different frequency components.

Frequency Analysis of Mechanical Waves Passing Through Cement Composites During the Early Hydration Phase

Presenting author(s):
Libor Topolar

Co-Authors: Mr Lubos Pazdera, Mr Michaela Hodulakova

Room: Mediterranean | 10:05 AM Wednesday, September 18, 2019

From the point of view of mechanical waves, hydration of cement-based composites is an intriguing and complicated process. After mixing cement with water (suspension phase), fine crystals form as a result of ongoing chemical reactions. These crystals then interpenetrate (plastic phase) and the cement therefore gradually hardens (solid phase). All hydration phases occur in a relatively short time interval. The experiments will utilise a short impulse generated by an ultrasonic generator that will pass through the fresh mixture. When evaluating these pilot experiments, we focused on the frequency spectrum, which is sensitive to the age of the concrete, the composition of the mixture and the formation of hydration products. During the individual experiments, parameters of the cement composite were changed (the water/cement ratio and cement type). Measurement of the internal temperature of the setting mixture is used as a supplementary indicator of cement hydration.

Continuous Wave Ultrasound Nondestructive Testing

Presenting author(s):
Mr Krassimir Stoev

Co-Authors: Mr Teguewinde Sawadogo

Room: Adria | 10:05 AM Wednesday, September 18, 2019

Currently, the primary method employed by ultrasound inspection system is based on applying pulsed sound/ultrasound energy to the inspected part, and detecting reflected/transmitted pulses. Typically, pulse-based methods are essentially time-domain back-reflection methods, and time-of-flight is the main measured parameter. Recently, continuous-wave frequency-domain back-reflection meters were developed in the radar and in the fiber optics fields, which demonstrate significantly better spatial resolution, higher SNR, and ability to detect reflecting objects at very short distances. The same approach was used to develop a prototype continuous-wave ultrasound inspection system. The parameters of the prototype system are described, and the advantages and limitations of the continuous-wave ultrasound inspection method are discussed. Examples of the use of the system are presented.

Additive manufacturing is considered to be one of the biggest industrial revolution of the last years. However, the extremely high thermal gradients involved in this fabrication process can induce internal defects, like porosity, lack of fusion and micrometric cavities. Therefore, process control remains a critical development topic in order to master the manufacturing. In this work, we propose a non-destructive sensor based on the lock-in photo thermal radiometry method, which could be implemented in situ for real time non-destructive testing and to prevent defective pieces manufacturing.
In the lock-in photo thermal radiometry method, a modulated power laser beam is used to heat the sample to study, and the emitted infrared thermal radiation is collected on an infrared detector. This thermal response can be described as an amplitude-modulated signal giving the phase shift of the thermal radiation with respect to laser heating power. This phase shift allows to deduce the thickness and the thermal diffusivity of the sample [1]. For an additive manufacturing piece, the measurement of phase shift variation can lead to the detection of a defect in the piece.
We demonstrate with our experimental setup the feasibility of this sensor for micrometric cavity defects detection up to millimetric depth of additive manufacturing pieces.
[1] New contactless method for thermal diffusivity measurements using modulated photothermal radiometry. S. Pham Tu Quoc, G. Cheymol, and A. Semerok, Review of Scientific Instruments 2014 85:5

Material Property Mapping using Ultrasonic Phased Arrays

Presenting author(s):
Ms Katy Tant

Co-Authors:

Room: Adria | 10:45 AM Wednesday, September 18, 2019

Typically, imaging algorithms within the ultrasonic non-destructive testing community assume that the probing waves travel at a constant speed within the material under inspection. This is a poor assumption when the medium is of a heterogeneous nature and it can result in misplaced and unfocussed defect reconstructions. Prior knowledge of the material’s internal structure would allow corrective measures to be taken and more reliable images to be obtained. The work presented here endeavours to map the spatially varying material properties of locally anisotropic, heterogeneous media using ultrasonic phased array measurements. This is achieved using the reversible-jump Markov Chain Monte Carlo (rj-MCMC) method; an ensemble approach within a Bayesian framework. Due to this Bayesian framework, a distribution of maps is obtained from which we can approximate the internal structure of our component and quantify the uncertainty attached to it. The resulting map can then be used in conjunction with an imaging algorithm to produce more reliable reconstructions of any embedded defects. Using simulated data, we show that this approach can yield a ten-fold improvement over standard NDT imaging methods in the sizing of a 3mm side drilled hole embedded in an austenitic steel weld.

Additive manufacturing (AM) techniques are used to fabricate parts layer-by-layer by fusing metallic feedstock. Removing many of the design constraints imposed in traditional manufacture allows AM components can have complex geometries. The AM process consists of many interdependent build variables which can lead to the development of parts with crystalline microstructures unsuitable in an engineering context. For example, most forms of AM encourage strong epitaxial grain growth in the vertical direction, leading to final components with high mechanical and magnetic anisotropy.
Spatially Resolved Acoustic Spectroscopy (SRAS) is a laser ultrasound technique, developed to non-destructively probe the mechanical response of crystalline materials by measurement of the surface acoustic wave velocity. In the context of AM, SRAS has been used to detect surface and sub-surface defects. In this presentation, two prominent forms of AM, laser powder bed fusion (L-PBF) and wire-arc (WAAM) will be discussed, focussing on characterisation of material texture and microstructure by measurement of the surface acoustic wave, using SRAS. These measurements will then be related back to the build process.
The talk will then conclude with remarks on the challenges posed by as-deposited AM surfaces for optical techniques, and demonstrate a build chamber compatible instrument. We will discuss the possibilities for defect and microstructure control, and the challenges remaining for online inspection.

Ultrasonic Inspection Using Multi-Axis Accelerometer

Presenting author(s):
Mr Yoshihiro Mizutani

Co-Authors: Mr Iori Suzuki, Mr Akira Todoroki

Room: Adria | 11:10 AM Wednesday, September 18, 2019

In recent years, the frequency band that can be measured by the accelerometer is getting wider. Though, it will be possible to measure elastic waves in the ultrasonic range with the accelerometer In the near future.
In this study, we investigated a method to reduce artifacts, which is often a problem in ultrasonic flaw detection, when elastic waves are measured with multi-axis accelerometers. Three kinds of reduction methods are proposed and its feasibility was examined using ultrasonic propagation simulation results.

Heat treatment is a central manufacturing step in component manufacturing in which the essential material properties are set and the component behaviour is determined. As a rule, the quality is checked today after heat treatment using more or less manual methods such as hardness measurements and metallographic cross section tests. The production step "heat treatment" and above all the associated quality assurance are to be brought into an industrially automated process under Industry 4.0. For this purpose, it is necessary to integrate suitable non-destructive test methods into the heat treatment process.
In the past few years, a number of research projects have developed essential components for the heat treatment processes of nitriding, tempering, annealing, bainitizing, forging and hardening. The continuous further development of non-destructive eddy current measurement technology provides a wealth of measurement data. It turned out that, in addition to the tried and tested methods of analysis and evaluation, the analysis of harmonics in particular proved to be particularly suitable. A complete analysis of the measuring task in advance is important in order to adapt and use the suitable parameters of the field strengths, coil structures, excitation and measuring coil dimensioning and design to be used, in order not only to obtain permanent measuring stability but also maximum sensitivity with regard to the essential parameters of the heat-treated material. The temperature-resistant construction of the coils plays a central role here, since the sensors are used directly in the heat treatment medium and must be resistant to aggressive media such as ammonia during nitriding, depending on the application.
It will be shown how eddy current measuring technology can be used in heat treatment furnaces and how the evaluation methods can already provide a large number of important material parameters online during heat treatment in order not only to automate quality assurance but also to gain new insights into the process of material changes during heat treatment.

Developments and Results with Scanning Acoustic Microscope

Recently nondestructive methods were based on handheld measurement, moving the ultrasound sensors manually. The hand of the specialist was one of the most important factors in finding the flaws in the materials. Combination of mechanically moved motion based on computer programs has changed the situation. Moving the heads with precision of 0.1 mm opens new era in ultrasound investigation, which is usually called scanning acoustic microscope, since the precise movement opened the way for much better resolution. Another advantage of program driven movement is its combination with ultrasound reflection, which produces 3D picture of inner part of the investigate material. There is growing number of such devices on the market now. We have developed a relatively cheap version, which opens this possibility for testing laboratories due to its price. We present results of investigated spot-weld, where the nugget had abnormal structure. Also mounted screws can be tested in-situ in nuclear reactors. One of our aims was to find imperfections in electronics, where minibubbles of size of less than 0.1mm could be seen, and also the electronics itself can be checked.

Ultrasonic Testing Residual Stresses and Structure of The Rails in The Area of The Welded Joint

Presenting author(s):
Mr Lyudmila Volkova

Co-Authors:

Room: Mediterranean | 1:00 PM Wednesday, September 18, 2019

The residual stresses appearance in the rails during production is linked to the metal temperature change during the heat treatment, hot deformation during the rolling and during welding, as a consequence, the steel microstructure changes. Change residual stresses strongly affect the rail service life. Changes of the structure in the zone of rail's welded reduce the fatigue life of the metal and can lead to the premature development of unacceptable defects.
The technology of stresses measurement in rails is based on the dependence propagation of ultrasonic waves velocity on mechanical stresses associated through acoustoelastic coefficients. Wave propagation velocities are determined by the results of the measurements the measured propagation times of shear waves orthogonally polarized. Two polarized waves are directed relative to the axis of the rail by the echo-pulse polarization-time method. Input and detection of shear waves are carried out using contactless electromagnetic-acoustic (EMA) transducer. The waves radiate normally to the input surface with the installation of an inputting and detecting sensor in the center of the rail head.
The specialized software allows observing simultaneously on the device monitor echograms of multiple reflections of two shear waves with mutually perpendicular polarization planes. Coherent time accumulation and autocorrelation processing are used in the program. It gets possible to provide an instrumental error of estimate stresses ± 2 MPa
For measuring Rayleigh and lateral waves propagation times is used the instrument with the autocirculation method .
The results of experimental measurements of the velocity of ultrasonic transverse, Rayleigh and lateral waves, and report the change in the velocity in the region of electrocontact and alumino-thermal joint welds in rails. Schemes for measuring ultrasonic waves using three types of structuroscopes are described. An increase in the velocity of ultrasonic waves is observed at the toe of the joint weld, this is due to the structural state in the heat-affected area, a sharp decrease in the wave velocity is observed at the center of the joint weld, this is due to the cast structure in this region. Types of waves are distributed depending on the structural sensitivity of velocities to the state of metal in the joint weld in rail.
The changes in the ultrasonic surface and lateral wave velocities near the head running surfaces of rails having carried various weld structural are studied. The surface and lateral wave velocities are found to correlate with the hardness and the structure of rail steel.

Characterization of Ceramic Composites by High Frequency Eddy Current techniques

Presenting author(s):
Dr Henning Heuer

Co-Authors: Ms Susanne Hillmann, Mr Martin Schulze

Room: Adria | 1:00 PM Wednesday, September 18, 2019

Eddy current testing is well established for non-destructive testing of electrical conductive materials. The development of radio frequency (RF) eddy current technology with frequency ranges up to 100 MHz made it possible to extend the classical fields of application even towards less conductive materials like CFRP, SiC and C-SiC based systems. It turns out that RF eddy current technology on CFRP generates a growing number of valuable information for comprehensive material diagnostic. Both permittivity and conductivity influence the complex impedance measured with RF eddy current devices. The electrical conductivity contains information about fiber texture like orientations, gaps or undulations in a multilayered material. The permittivity characterization influenced by dielectric properties allows the determination of local infiltration quality. An explanation for that effect is seen in the measurement frequency range and the capacitive structure of the composite structure. Using radio wave frequencies for testing, the effect of displacement currents cannot be neglected anymore. The capacitive structures formed by ceramics is supposed to further strengthen the dielectric influences on eddy current measurement signal. Due to electrical field effects, also nonconductive materials like resins can be inspected by RF techniques. Maxwell’s equations, FEM simulations, and experimental research are applied to support this hypothesis. An industrial high-frequency eddy current (HFEC) device is used to measure the change of dielectric properties during the curing process of the epoxy resin L20. The measurement results are in good agreement with the expected behavior of the parameters relative permittivity and tan δ during cure. Using a capacitive reference device, similar characteristics regarding the change of the complex permittivity of the resin can be observed. In addition, HFEC imaging results on PMMA are presented, discussed and compared to capacitive imaging. HFEC permittivity mapping benefits from a high spatial resolution with a sensitivity and penetration depth that is at least comparable to those of capacitive imaging technology. The paper closes with an introduction to robot based systems for radio frequency imaging on real 3D structures.

A Study on The Applicability of Ultrasonic Guided Waves for Monitoring Damage Development in The Foot of In-Service Railway Rails

Presenting author(s):
Dr Michele Carboni

Co-Authors:

Room: Mediterranean | 1:25 PM Wednesday, September 18, 2019

Railway rails are safety components whose failure can lead to dramatic consequences. The peculiarity of rails is that they can fail in many different ways: some of them interest the whole rail section, while others just a part of it (the head, the web or the foot). Moreover, bolted and/or welded joints can represent critical preferential initiation sites of damage.
Due to the very high number of kilometers of in-service rails, it is not feasible to send teams of operators to inspect periodically all of them: the generally adopted strategy is to run diagnostic trains, usually instrumented with UT equipment and other measurement means, all along the lines and send teams of operators only to those sites showing possible anomalies. On the other hand, one of the main open points of UT inspections carried out by the diagnostic train is that the foot cannot be inspected at all because it is not accessible by the probes typically applied to the rolling surface of the head.
The present research focuses on the implementation, based on experimental and numerical activities carried out in the lab on long rail chunks containing defects with different shapes and sizes, of a permanent monitoring system devoted to the evaluation of the integrity of the rail foot. The approach uses ultrasonic guided waves actuated and sensed by piezoelectric sensors along with a post-processing procedure defining a simple, but relevant, damage index. Both the cases of free and constrained rail are considered, studied and discussed.
Results seem very encouraging, so that the next step of the research is going to be the on-field application.

The Optimal Surrogate Synthesis of Circular Surface Eddy Current Probes with a Uniform Sensitivity in the Testing Zone

Presenting author(s):
Mr Ruslana Trembovetska

Co-Authors: Mr Volodymyr Tychkov, Mr Volodymyr Halchenko

Room: Adria | 1:25 PM Wednesday, September 18, 2019

The all types of surface probes have the property of unevenness sensitivity due to the non-uniform of the eddy currents density distribution (ECDD) in the testing object (TO) for any excitation coils types. This deficiency makes the difficulties in solving defectometrics problems by EC method, namely the identification of the geometric dimensions and defects shape based on the measurements results. In even more, this effect develops itself in moving TO and probe relative to each other, due to the transfer current influence. To repair it, is possible, by using the coils complex, arranged in a certain space way included counter/according and representing excitation EC system. As a result, the system provides uniform of ECDD on the testing zone surface, and, consequently, a uniform sensitivity. This research focuses on solving the inverse problem of optimal parametric synthesis uniform of ECDD in the testing zone circular surface ECP based on the velocity effect. To solve the synthesis problem uses an mathematical EC testing process model, which takes into account the moving speed of the flat object unlimited length and width, its thickness and the electric-physical parameters of the TO. The model contains multiple improper first kind integrals, the repeated calculation of which is very resource-intensive for the computing and time-consuming, and this makes it impossible to solve the optimal synthesis problem by standard means. In a research carried surrogate synthesis probes with uniform sensitivity, which uses substituent target function. For these purposes are constructed neural network RBF- and MLP-metamodels circular surface ECP. To improve the metamodel accuracy used composites and neural network ensembles, as well as domain decomposition to find a solution. On numerical examples illustrate the proposed metamodels effectiveness, shown them enough high accuracy, and low resource consumption, allowing to realize the optimal surrogate synthesis probes. For the synthesis, we used a population metaheuristic particle swarm optimization algorithm with evolutionary swarm forming composition, which is a low-level hybridization of the genetic algorithm GA and PSO algorithm, highly convergent in solving problems with many variables.

Recently, various guided wave tomography algorithms have been developed to map structural changes from remote locations. The focus has been on structures made of isotropic materials and little work has been done on structures made of anisotropic materials. Primary complication to implement tomography in composite laminates is associated with the complex forward model to accurately simulate the 3-D guided wave propagation. In this study, we demonstrate that guided wave propagation can be approximated by an equivalent 2-D acoustic model. It is based on finite-difference discretization method in which the wave-field is parametrized by phase velocity and dimensionless anisotropic parameters. These parameters control the velocity dependence on propagation direction. The reconstruction of defects is based on a full-waveform inversion algorithm and was implemented on the data obtained from finite element simulations. Results on a localized stiffness defects in composite plates with various layups demonstrate the attractiveness of the proposed methodology.

Evaluation of The Influence of The Phase Precipitates on The Signals of Pulsed Parasite Currents - PEC in Superduplex SAF 2507 Steels Submitted to Thermal Treatments

Presenting author(s):
Mr Joao Queiroz

Co-Authors:

Room: Adria | 1:50 PM Wednesday, September 18, 2019

The need for more resistant materials for the offshore environment has raised a category of steels with superior characteristics to the ferritic and austenitic steels. Superduplex stainless steels have been developed for this purpose and are widely used in the chemical, petrochemical and pulp and paper industries, presenting high mechanical and pitting corrosion resistance. During service, these materials are subjected to high temperatures where microstructural transformations can occur, like the precipitation of different phases, which promote the reduction of tenacity and resistance to corrosion.The non-destructive tests appear as an aid tool to detect and characterize these alterations. In this work, the non-destructive test by PEC (pulsed eddy current) was applied to SAF 2507 steel samples exposed to thermal treatment of solubilization at 1120ºC and isothermal aging at 900ºC at different time intervals in order to evaluate the influence of precipitates of intermetallic phases in the signals.Metallographic tests, optical microscopy and scanning electron microscopy were realized to visualize the microstructure present in the test samples after the heat treatment.

Transient Amplitude Analysis of Lamb Wave Mode Generated by EMATs

Presenting author(s):
Mr Kenji Kitamura

Co-Authors: Dr Toshihiko Sugiura

Room: Mediterranean | 2:15 PM Wednesday, September 18, 2019

In this study, we transiently analyzed the amplitudes of several Lamb wave modes generated by electromagnetic acoustic transducers (EMATs). In non-destructive testing (NDT), ultrasonic testing using Lamb waves is efficient for inspection over long distances. However, in inspection using Lamb waves, the number of modes increases with increasing frequency, and these are very complicated. The excitation of the material by the transducer generates multiple Lamb wave modes, but there are few studies which determine the amplitude for each mode theoretically. The determination of the amplitude of each mode excited by the transducer is necessary for highly accurate inspection. In order to excite a specific mode, a trial and error method has often been adopted by giving an excitation closely matching the steady-state amplitude distribution of each mode at the surface of the material. On the other hand, EMATs have high mode selectivity by tuning the coil pitch. However, even EMATs cannot generate only a targeted mode but also untargeted modes. In this research, the amplitudes of the Lamb waves generated by EMATs were obtained theoretically. The skin depth of the eddy current in the material by EMAT is quite small, and EMAT acts only on boundary. Under this assumption, the amplitude of each Lamb wave mode just generated can be estimated by Fourier transform. Furthermore, the steady-state amplitude of the propagating Lamb wave mode cannot be determined in the excitation region where EMAT is placed. We performed transient analysis considering the amplitude increases with the propagation in the excitation region.

Recent years have witnessed the emergence of new materials as well as innovative manufacturing technologies. The confluence of these two developments will have a major impact on several sectors of our manufacturing economy including the aerospace, automotive, energy and transportation industries. Advances in nondestructive evaluation (NDE) need to march lockstep if these developments are to have an impact. Accurate, reliable and quantitative NDE characterization of materials is vital if we are to make any progress. Compared to the other widely used non-contact NDE techniques such as radiography and air-coupled ultrasonic testing, electromagnetic NDE methods offer unique benefits including high-speed, need for single-side access only and relatively low cost. This paper presents an overview of electromagnetic NDE techniques that are tailored to address three formidable application challenges. We first present a method for multi-sensor characterization of damage in components made of composite materials which are inherently anisotropic, have complex structural geometries, and designed to operate in hostile environments. The paper presents an integrated diagnosis and prognosis framework to achieve the goal. Second we present a multi-frequency, high-Q, EM sensor with super resolution capability for inspecting additively manufactured metal (AMM) components for characterizing defects during the manufacturing process. Last, we present a nonlinear eddy current sensor for characterization of case-hardened components. Results demonstrating the performance of these sensors are presented.

A Case Study on Ultrasonic Characterization of an Austenitic Weld – Is ‘In Situ’ Feasible?

Ultrasonic inspection of complex structured materials is often hindered by beam deviation and scattering-induced noise and attenuation. Usually, the choice of inspection parameters relies on representative mock-ups which help establishing optimal performance with regard to the critical characteristics mentioned above. However, the underlying assumption, that mock-ups fabricated using the same manufacturing procedures are identical in terms of their micro- and macrostructure, is not necessarily verified. To support inspection practice, it is desirable to be able to assess material characteristics in the field. One of the ambitions of ADVISE – a European H2020 project - is to develop in-situ characterisation techniques for two problem categories: for the inspection of welds, a technique based on the analysis of travel times and a parametric weld model aims to reconstruct the macrostructure of a weld; for bulk materials, such as cast austenitic stainless steel, the project attempts to gain information about the microstructure in terms of the average grain size and possibly to estimate the grain size distribution. The outcome of the characterisation is expected to serve the following purposes: in the case of welds, it enables beam deviation to be accounted for when interpreting ultrasound signals, leading to more precise defect localisation; for bulk materials, the grain size estimate indicates the inspectability of the component in terms of the expected signal to noise ratio.
In this contribution, we present results obtained from a weld characterisation exercise, for which an actual circumferential weld joining two stainless steel pipes was manufactured according to realistic specifications. Following a series of ultrasonic measurements, we estimated both the grain orientation map of the weld and the average grain size across the entire sample including the parent metal. As a ‘ground truth’ reference, we used two different approaches to predict weld formation and analysed metallographic images. Discussing the results and a variety of practical issues encountered, we debate the feasibility of ultrasonic characterisation of welds in situ.

The feasibility of remote imaging of damage by using resonant airborne acoustic activation combined with laser vibrometry is studied experimentally. Two-step optimization to stimulate the damage vibration comprised resonant oblique incidence followed by frequency selective local resonance in the damaged area (LDR). The methodology comprises the two sets of piezoelectric loudspeakers which cover the frequency range up to 45 kHz and provide the sound pressure level 90-120 dB. These airborne sound pressure levels are found to be sufficient for remote excitation and laser vibrometry imaging of disbonds, delaminations and impacts in composites. Various types of damage are shown to manifest LDR in two different ways depending on the structure of the damage. The resonance is activated either as in-phase vibration over a total damaged area at a single frequency (normal LDR) or includes weakly coupled resonant vibrations of its parts at different frequencies. In the latter case, LDR is a combination of multiple so-called fractional resonances. Both kinds of the resonances enhance the sensitivity of remote defect-selective imaging and are applicable to a wide range of flaws. Despite the relatively low airborne acoustic pressure the resonant technique operates well for not only strong loose damages but also for subtle defects with tightly-packed fragments including barely visible and even virtually invisible damages in various scale and shapes composite parts.

Ultrasound Testing of Emerging Joining Methods in Automobile Industry

Presenting author(s):
Dr York Oberdoerfer

Co-Authors: Robert Kitzmann

Room: Mediterranean | 3:20 PM Wednesday, September 18, 2019

Ultrasound testing of spot welds on car bodies and body parts is a well-known application in the automotive industry since spot welding is still the most important joining method in this industry segment. However, the general trend for lightweight construction resulting from legal requirements for better fuel efficiency brings forth the necessity to join metals with e.g. new metal grades or even materials that have not been used in automotive serial production before. Since joining dissimilar metals and/or materials by spot welding is either highly difficult or completely impossible, other joining methods like gluing and projection welding with subsequent screwing becomes more and more important and thus the necessity to non-destructively test these joints.
In this presentation, the ultrasonic inspection of these emerging joining methods will be reviewed and requirements on the ultrasound instrument with respect to its normal use discussed. Examples of applications will be presented, where alternative joining methods with different material combinations were successfully tested by means of ultrasound.

In recent years, there has been a surge in the number of academic research groups and commercial companies exploiting naturally-occurring cosmic-ray muons for Non-Destructive Testing purposes. Typical applications involve thick, shielded containers and/or large, complex structures that cannot be adequately investigated using conventional inspection techniques. This field, called muography, make global news in November 2017 when a Franco-Japanese research team discovered a hidden chamber within the Khufu Pyramid in Egypt.
The University of Glasgow is one of the pioneers of this imaging technique in Europe. It uses fundamental, charged particles called muons that are produced in the upper atmosphere from cosmic-ray interactions. Muons are observed at sea level with a flux of approximately one per second for an area the size of the human hand. By tracking these particles through an unknown structure using pairs of position-sensitive detectors, a 3-dimensional density distribution of the constituent materials can be reconstructed with positional accuracy and resolution of less than a centimetre.
Lynkeos Technology is an award-winning Scottish company that spun-out from the University of Glasgow after a research programme funded by the UK Nuclear Decommissioning Authority. In September 2018, the Lynkeos Muon Imaging System was commercialised under Innovate UK funding and the first unit was installed on the Sellafield site in the UK to characterise the contents of nuclear waste containers. Results from UK Nuclear Industry imaging trials on legacy waste drums and vitrified waste products will be presented at ISNDCM 2019.
In parallel, Lynkeos Technology is evaluating the capability of its entirely-passive technology for new applications across a range of different industries. These include the monitoring of spent fuel dry storage casks for international safeguards, pre-decommissioning safety assessments of large-scale nuclear facilities and structural health condition monitoring of civil infrastructure such as bridges. Simulation results from selected applications will also be presented to demonstrate the vast potential of this emerging NDT technique.

Resistance spot welding is one of the main joining processes in mass-manufacturing sheet assembly industries including automotive, appliance, construction. In spite of the fact that weld controllers ensure proper current/heat delivery into the weld spot, still there is no universal way for the robot to tell the quality of weld joint in real time. After more than 35 years of successful application of robotic spot welding in the industry, the quality of welded joints is still determined in post-process evaluation. All current means of ensuring the proper functioning of robotic spot welders are indirect and based either on measuring current, voltage, force and displacement, or selective post-welding inspection of the formed joints. Both approaches are not satisfactory for quality demands of the automotive parts assembling industry.

Recently, the Institute for Diagnostic Imaging research (IDIR), University of Windsor (Windsor, Canada), has developed an ultrasonic spot weld monitoring system prototype for automatic real-time quality inspection of the spot welds. The NARMCO Group (Windsor, Canada), as the IDIRs industrial partner, expressed interest in customizing and testing the system prototype by installing it at one of the NARMCO plants (PMS in Gadsden, AL, USA). The goal of the project is to validate the system prototype at the assembling line and as a result of this trial is to confirm current algorithms and technical solutions, and at the same time to establish next strategic steps in further development of new system.

Modal Analysis Via Impact-Echo on Concrete Reinforced Slab

Presenting author(s):
Mr Richard Dvorak

Co-Authors: Mr Lubos Pazdera, Libor Topolar, Mr Tomas Luks

Room: Adria | 3:45 PM Wednesday, September 18, 2019

Concrete is advanced building material, which fulfill the major role in the field of materials used for construction worldwide. Its ability to create monolithic structures and prefabricated elements is based on the versatility and wide range of admixtures, which can modify concrete properties for each role. In past decades a growing economic price of one of the base components of concrete – cement – push manufactures to use more latent hydraulic additives such as blast furnace slag or fly ash to substitute an expensive cement.
Other hydraulic materials which can substitute concrete is alkali activated materials, which are based on reaction of suitable aluminosilicate precursor with alkaline activator (AA). The resulting structure depends on the type of used aluminosilicate precursor, curing conditions or alkaline activator used and its dosage.
One of the most elegant way to test solid elements on presence of defects or crack is modal analysis conducted by Impact-Echo nondestructive method. This method is widely used in aeronautics and mechanical engineering but finds a usage also in the research field in civil engineering.
Presented paper describe a calibration of modal analysis via impact echo method performed on reinforced concrete slab. The slab was after initial testing exposed to high temperature to simulate a defect in its structure. These results are part of preparation to use modal analysis on slab manufactured using an alkali activated mixture.

Evaluation of TOFD Capabilities for Ultrasonic Detection and Characterization of Planar Type Defects in Thick Welds

Conventional and phased array UT TOFD techniques are used, as an alternative to radiography, for end of manufacturing NDT on ferritic thick welds of Nuclear Power Plant heavy components, at FRAMATOME / CM (Chalon - St Marcel factory in France).
These examinations aim at checking the absence of unacceptable flaws (planar type, large elongated inclusions or wide porosities clusters) in the whole weld and HAZ volume.
For such thick components (up to 180 mm), several TOFD set-ups are used. Moreover, as some parts of welds exhibit restricted access, asymmetric TOFD system has been developed. Besides, the defects likely to appear may be oriented in many ways regarding the UT beams direction.
The examination performances have been demonstrated against the RT ones in an equivalence type process (relative comparisons) and for limited cases.
The Engineering (DTI) and the Research & Development (IB) departments of FRAMATOME have launched a complementary study to quantify in details these overall actual performances of the TOFD equipment used at Chalon-St Marcel.
The scope covers the ranges of defect characteristics (orientation, size…) for detection and characterization purposes. Practical tests with different TOFD set-ups (symmetric and asymmetric) on mock-ups and simulations are intended.
This paper focusses on the results in terms of detection versus flaw orientation (mostly skew type rotation) and planar classification versus signal phase behavior.
It also presents the final procedure to be issued, which shall encompass all the justifications and the explanations of the observed phenomena, whatever the configuration of interest.

Synthetic fiber rope has high specific strength and modulus compared to metal wire rope. Though the synthetic fiber rope is used for the machines that need to be lightened, such as wire-driven robots, it is known that the longitudinal elastic modulus of the rope changes with loading history. Therefore, the in-situ and non-destructive method to monitor longitudinal elastic modulus of the rope is desired. On the other hand, it is well known that the longitudinal elastic modulus of a metal narrow-rod can be calculated from elastic wave velocity when the density of the material is known. Although, the density of the rope also changes with loading history and then, the modulus cannot be estimated by the general ways.
In this paper, to solve the problem, we propose to use the unit of “tex” which is defined as the mass in grams per 1,000 meters and express the unit of the longitudinal elastic modulus of the rope as “N/tex”. The “tex” is known as linear density and used in the synthetic fiber fields. The longitudinal elastic modulus of the rope is estimated by the velocity of the elastic waves with lower frequency in this study. Feasibility of the proposed method is evaluated by comparing the estimation results and experimental results which are directly calculated from measured load and elongation. The comparison results show the proposed method can be used to qualitative evaluation of the longitudinal elastic modulus of the rope.

NDE of Friction Stir Welds

Presenting author(s):
Dr Bernhard R Tittmann

Co-Authors:

Room: Mediterranean | 4:35 PM Wednesday, September 18, 2019

Ultrasonic interference fringes are used to image weak bonds associated with friction stir welds. Frequencies in the range from 400 MHz to 1000 MHz are used to generate incident and reflected leaky surface waves to mark the friction stir welds bonds. Tensile tests verify the observed weakness of the bonds. Parallel calculations simulate the interference of surface guided waves at a weak bond line.

Improvement of Safety of Nuclear Power Plants Equipment’s by Using the Project Of «Cracks Under Control»

Presenting author(s):
Dr Ayman Abu Ghazal

Co-Authors: Dr.Vitaly Surin

Room: Adria | 4:35 PM Wednesday, September 18, 2019

The “cracks under control” project was recently released by the laboratory ElphysLAB in National Research Nuclear University MEPhI, Moscow. It is a future proposal to reduce the accident rate situation which may arise during use of the equipment of NPP, due to the action of the loads and the occurrence of various types of cracks in the most sensitive parts of nuclear power plants equipment. The essence of the current project is based on a new non-destructive testing method which called scanning contact potentiometry (SCP).
In the current report, the prospects and advantages of using the «crack under control» projects have been discussed as an integrated system for improving the safety of various types of equipped nuclear power plants. Furthermore, the results obtained by the proposed study confirm that the application of the «crack under control» project is considered as a part and parcel of the safety of modern nuclear power plants.
By using the SCP method, it is possible to obtain advanced information on the state of nuclear facilities in the absence of access from personnel where there are large radiation doses during operation. The development of integral system based on the «cracks under control» project will be as a warning bell, which reports about the status of nuclear power plant equipment during operation with minimal costs.

Acoustic Emission Supported Monitoring of Fire Spalling of UHPFRC

Presenting author(s):
Mr Aljosa Sajna

Co-Authors: Martin Schneider, Friderik Knez

Room: Mediterranean | 8:10 AM Thursday, September 19, 2019

Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) is a family of the most rapidly developed cement bounded materials which has the prospect for being used in sustainable concrete technology. Comparing to ordinary concrete it’s characterized by extremely dense cement matrix and enhanced ductility. Due to these unique characteristics its response to fire and high temperatures seems to be significantly different compared to ordinary concrete. The mechanism of fire spalling of UHPFRC hasn’t been thoroughly investigated and adequately explained, yet.
Monitoring of UHPFRC spalling at high temperatures is crucial for explaining the spalling processes of those materials. But monitoring of fire spalling of any kind of concrete during fire test is from the experimental view very challenging.
In the investigation presented in the paper acoustic emission supported monitoring of fire spalling of UHPFRC is presented and discussed.
In the preliminary research plates (50 x 50 x 20 cm) made of five different UHPFRC mixes were exposed to ISO 834 fire test. During the whole period of temperature increase the spalling of concrete was monitored by the acoustic emission (AE) techniques, following the RILEM TC 212-ACD recommendations. Simultaneously the temperatures in different depths were measured.
By visual inspection of the plates after the tests surprisingly large differences in the performance of five UHPFRC mixes during the temperature increase were observed; the resistance to fire of the UHPFRCs tested highly depend not only on the quantity of PP-fibres but also on the aggregate size.
In the paper the AE based spalling monitoring result are methodically analysed through different AE parameters (number of events, acoustic energy, amplitude, rise time…) and compared to visual damage of the plates. The experiences gained are systematically discussed.

Acoustic Emission (AE) acquired increasing interest in the last decade as an assessment and monitoring tool for the safety and reliability evaluation of reinforced concrete structures, historic and masonry buildings. The application of the AE technique in the civil engineering field,however, requires to overcome various issues related to several factors such as: structure complexity, non-homogeneity of the concrete material, attenuation of the signal, environmental noise. However,
in the last years, considerable efforts have been made in the assessment and interpretation of AE data. Multivariate statistical analysis was applied effectively to manage AE data and to discriminate relevant feature related to main damage mechanisms in concrete. Principal component analysis (PCA) and artificial neural networks (ANN) was recently applied with promising results.
However, a fundamental limitation of these numerical methods is the not used friendly and the need of a suitable scientific expertise on the topic to define and discriminate the clusters. In such a context, in order to assess the damage severity of a structure under loading conditions, more user friendly statistical methods (z, RA, b and Ib value) on AE data can be applied. Furthermore, calm ratio, load ratio, severity and historical index are statistical parameters that give information on the damage level of the structure and consequently can be used easily as damage evolution indexes for civil engineering components. This work gives a brief discussion of the use of the acoustic emission for the health monitoring of reinforced concrete structure beam. Acoustic emission signals were acquired using an AMSY-6 Vallen machine, coupled with 12 high sensitive acoustic sensor Fuji AE105A in order both to perform a source localization and to acquire a test waveforms. A continuous recording was performed, in order to
acquire the acoustic events generated during loading and loading cycles up to the failure on a pre stressed concrete beam. A real scale size beam (length of 6.30m and a cross section of 0.40×0.25 m2) has been used for this investigation and the AE signal processing are the main principal data in this work for assessing by using the statistical technique, which is known as intensity analysis method (IA). The correlation among the different parameters will be performed in order to better discriminate their potentiality and to identify the levels of criticality
of the structure otherwise not identifiable by a single parameter.This technique was applied with effective results in order to quantify and evaluate in a user friendly approach the damage severity on concrete structures.The variation of the acquired parameters during time can be then considered as an affordable and reliable indicator of the degradation in specimen surface.

Recycling of construction materials is crucial for sustainable development and for meeting the requirements imposed by governments on preserving natural resources, e.g., European Union laws banning landfilling of all inert materials from 2024. Traditionally, concrete rubble was either disposed in landfills or crushed and used as filling if there was a demand in the vicinity of demolition sites. However, when used as filling or backfilling, its potential is not fully exploited. Our research is focused on modeling and design of cementitious composites with 50% replacement of Portland cement by finely ground recycled concrete.
This contribution presents the non-destructive DIC-based method for assessment of stiffness gains during hardening of the pastes containing recycled concrete. Using a camera and own tailored DIC codes written in Python, we were able to perform modal analysis of slender beams to evaluate Young’s modulus. Such an approach allowed to perform continuous measurement on the same specimens without a need for commercial software packages.
The analysis revealed that the recycled concrete fines acting as a micro-filler capable of densifying the cementitious matrix and interfacial transition zones around aggregate, can increase the stiffness of composites and contribute the early stiffness gains.

Recycling of demolition waste to ensure economic and environmental sustainability in the construction industry has become a worldwide issue. Concrete, being the most abundant construction material, constitutes the biggest portion of that waste. The primary effort of the newly established environmental laws is focused on a maximum possible replacement of primary materials, such as Portland cement and aggregates, in concrete production. In order to eliminate strength losses associated with the incorporation of concrete waste into the newly produced material, a study on the performance of industrial by-products, such as fly-ash or blast furnace slag, has been carried out.
The results indicated that a proper composition of the cementitious matrix could lead to utilization of the recycled material without sacrificing the structural performance. Moreover, it was found that shrinkage and creep of the matrix are lower, compared to ordinary Portland cement paste.
To reveal the mechanisms responsible for the shrinkage and creep reduction, assess the material parameters related to these phenomena, and test the performance of pastes in the vicinity of stiff inclusions, we employed digital image correlation (DIC). In particular, an image registration algorithm based on discrete Fourier transform was implemented in an in-house open-source software, connected to commonly available hardware. The system can be used for monitoring of displacement in real-time with up to 60 Hz sampling rate and is scale independent. Therefore, its use in structural health monitoring, quality control, or laboratory testing is envisaged.

High Temperature Hydrogen Attack (HTHA) is an intergranular damage mechanism that occurs in some steels when exposed to high partial pressure of hydrogen at elevated temperatures. The presence of microstructures that contain carbides, while helping the steel’s mechanical properties, also contribute to the initiation of HTHA. At elevated temperatures, typically above 400 oC, and partial pressures, atomic hydrogen (H) can diffuse into steel. At grain boundaries, crystal imperfections, inclusions, discontinuities, and other defects, the atomic hydrogen reacts with dissolved carbon or with metal carbides forming methane.
Because methane molecules are too large to diffuse through steel, the methane accumulates forming high-pressure micron-size bubbles that continuously grow (by creep due to pressure from the trapped methane) and coalesce into fissures along grain boundaries. In more advanced stages of HTHA, these diffuse fields of micro-fissures continue to grow and coalesce into form larger tears, i.e., cracks (0.1-1.0 mm) along the grains and often along inclusions in the rolling direction. The chemical combination of carbon and hydrogen also results in decarburization of the steel, i.e., loss of carbon from the steel, which in conjunction with the presence of the methane bubbles and fissures, change the mechanical response of the steel.
A non-collinear ultrasonic wave mixing approach capable of nondestructively evaluate and assess high temperature hydrogen attack (HTHA) damage in carbon steel pressure vessels is presented. Measurements were performed on test sample extracted from a pressure vessel retired from service. It was observed that the nonlinear ultrasonic measurements are consistent with the damage observed using scanning electron micrographs and with the mechanical response of tensile test samples extracted throughout the pressure vessel wall thickness. Results show that the non-collinear ultrasonic wave mixing approach has the potential of detecting and assessing the level of HTHA damage through the thickness of pressure vessels while still at microscale level. The method only requires access to the vessels’ outside surface, which makes it very attractive for field inspections.

Non-Linear Spectroscopy Measurement on Thermally Damaged Concrete

Presenting author(s):
Mr Jan Patera

Co-Authors: Mr Zbynek Hlavac, Mr Jindrich Jansa

Room: Mediterranean | 10:30 AM Thursday, September 19, 2019

Aim of this article is monitoring of concrete degradation. Concrete samples were subjected to different levels of thermal load. After that, a set of concrete prisms was tested by non-linear spectroscopy methods. Non-linear spectroscopy is based on measuring the elastic-plastic response of the material whose plastic component is caused by microcracks. Numerous microcracks caused by thermal damage increase non-linear response of the test specimen. Two particular methods were selected – Non-linear Wave Modulation Spectroscopy (NWMS) evaluating the intermodulation distortion and Non-linear Resonance Ultrasonic Spectroscopy (NRUS) measuring the frequency response for several different amplitudes. Both test methods were able to demonstrate and to assess the degree of damage to the concrete. They exhibited clear dependence on tensile strength or compressive strength and seem to be a very sensitive indicator of the material condition.

The components operating in aggressive environment like corrosive fluids, high temperature and stresses undergo corrosion and corrosion related degradation. One of the significant degradation factors in terms of integrity is erosion-corrosion in piping systems and creep in high pressure pipelines of thermal power plants. Prompt detection and assessment of high-temperature deformation and damage process before failure takes place is most important. Non-destructive testing plays a very important role in providing detection of the early signs of corrosion so that corrective action can be taken before damage becomes severe.
This article is focused on analysis of a set of steam piping samples with different degrees of degradation and heterogeneous laboratory weld joints coming from creep tests by acoustic emission (AE) method using their locations and extracted AE parameters. This method is a widely used non-destructive evaluation technique mainly during periodic testing to insure structural integrity of process plant equipment. It is also very useful in material research. Sources of AE include many different mechanisms of deformation and fracture, in case of creep, such as strain hardening, recovery, precipitation of carbides, cavity formation, etc. In this study, time domain and frequency domain characteristics of AE signals generated by different creep mechanisms are presented. The main task is to find a relationship between crack creation and propagation and AE response. An integral part of this study is also the analysis of noise and other interfering signals coming from outside. Since cracks may grow and propagate very quickly, thus causing sudden failure of the component, it is of paramount importance to be able to detect creep damage in its early stages.

Characterization of Conductive Deposits on Steam Generator Tubes Using Typical Eddy Current Technique

Presenting author(s):
Mr Valery Lunin

Co-Authors:

Room: Mediterranean | 11:20 AM Thursday, September 19, 2019

Knowledge of the deposit condition within a steam generator (SG) is valuable for assessing its impact on the potential for accelerated corrosion of the heating surfaces. Any layer of conductive deposits around the tube wall decreases the heat transfer in the SG and thus reduces its operational efficiency. Therefore it is useful to characterize the total deposit volume in the SG to plan the chemical cleaning operation. It is also useful to check afterwards the efficiency of the cleaning process. This paper presents method to evaluate the average thickness of deposit on tubes based on eddy current (EC) inspection with a standard bobbin coil, routinely used for the inspection. The method comprises creating a calibration curve having at least three regions of deposit material with different thickness and EC signal reflected from these regions is used to obtain the required curve. Evaluation of conductive deposits is carried out simultaneously with conducting typical automated eddy current inspection procedure by multi-frequency method. To determine the geometric parameters of conductive deposits, first of all the program PIRATE according to certain criteria finds the location coordinates of conductive deposits. Then this program determines the length along the axis of this region through the scanning step and the number of samples. The effective value of low-frequency signal in absolute mode is calculated as a root of the sums of the squares of real and imaginary components of the signal, related to the amount of samples. Thickness of conductive deposit layer is processed through calibration curve.

Receiving More Realistic Crack Signals for Calibration Eddy Current Inspection of Tubes

Presenting author(s):
Mr Valery Lunin

Co-Authors:

Room: Mediterranean | 11:45 AM Thursday, September 19, 2019

Requirements for eddy current (EC) inspections of WWER steam generator heat exchanging tubes are becoming increasingly stringent. The traditional industry-standard method of comparing inspection signals with defect signals from simple in-line calibration standards is proving to be inadequate. One cause of inaccuracies is that the calibration tube defects do not realistically represent the actual in-service tube cracks being characterized. For more complete understanding of EC field interactions with stress corrosion cracks and other anomalies is required for the industry to perform consistently reliable inspections. Finite element modeling is a valuable tool that is continually improving the reliability of EC signal analysis. Results from modeling can help inspectors to properly discriminate between real defect signals and false call, and improving reliability in crack sizing. To properly evaluate depth of cracks, EC probe signals should be compared with more realistic crack geometries than those used in standard calibration tubes. This paper discusses examples in providing more realistic crack signals with which EC probes can be calibrated.

Nondestructive testing of open-die forgings is indispensable to guarantee high quality of such products. UT-testing has been implemented into the production chain as means of quality since the 1950’s. Furthermore, the detection of surface and subsurface defects can be performed by eddy current techniques. For the last 40 years, Fraunhofer Institute for Nondestructive Testing (IZFP) has been developing the 3MA-technique (Micromagnetic Multiparameter Microstructure and Stress Analysis), that combines four techniques of measuring electric and magnetic effects in the sample. By means of Barkhausen Noise, Eddy currents, harmonic analysis and electromagnetic interference permeability the correlations between magnetic properties such as coercitivity and magnetic permeability on one hand and hardness, tensile strength and residual stresses on the other hand are defined. The measurement of hardness by application of 3MA-technique has been standardized in several guidelines.
Saarschmiede Freiformschmiede (SSF) is continuously developing and implementing NDT-techniques into its process chain to ensure highest product quality. The co-operation with Fraunhofer IZFP permitted to correlate 3MA-signals to mechanical properties measured destructively by tensile testing. High accuracies between destructive and non-destructive determination of tensile properties have been observed during first examinations.
Implementation of 3MA-technique into SSF’s production chain permits shorter lead times due to fast pre-evaluation of mechanical properties before final inspection by destructive techniques.
This paper deals with newest measurements on shafts made of creep-resistant steels and steel grades that are tough at low temperatures. Different calibration modes and both advantages as challenges in achieving a reliable calibration for this testing method will be presented.

Transient radar method (TRM) is introduced as a novel method that is capable to analyze electromagnetic properties as well as geometrical parameters of multi-layer structure simultaneously. In this paper complex permittivity as well as thickness of each sample are extracted by means of TRM experimentally. This study focuses on the minimum depth resolution that is detectable by TRM. So ultra-sub-wavelength depth resolution is tested experimentally. Three PVC sheets with different thicknesses will be used as sample under test. The thickness of these PVC sheets are 2, 1 and 0,3 mm which are corresponding to (λ/15), (λ/30) and (λ/100) respectively (λ is the wavelength in free space). The carrier frequency is almost 10 GHz and experiment was done in bio-static radar style and in free space environment. Single ended structure of TRM is using in this experience. Some of error sources such as switch leakage and non-perpendicular illumination as well as stochastic errors are considered. The novel technique has the potential for deployment in a wide range of applications ranging from the textile industry, wind energy industry, automotive, biotechnology, food industry, pharmacy as well as somewhere that high rigid material such as metallic sheets are coated by means of soft material like plastics, foams, paint and so on, because of traditional methods such as radiography are not efficient to be used.

The inspection of the steel sphere legs that hold up gas storage spheres has been difficult because of the thickness of cement that is applied to the legs to make them “fireproof”. The cement contains steel studs that are welded to the legs and wire mesh that may vary in mesh size, all of which complicate the inspection possibilities. A new, low frequency AC advanced scanning technique has been developed which can detect corrosion under fireproofing (CUF). The technique and its industry-supported development is described.

The high tensile strength steel sheets are usually used after pressing for the products such as automobiles or electric appliances. For the stable pressing, the steel sheets with uniform mechanical properties are strongly required. Among the several mechanical properties, the yield strength affects the ability of pressing and knowing the yield strength for the entire length of steel strip coil enables to decrease the unevenness of mechanical properties inside the coil and raise the quality of our products.
The magnetic properties of steel are related to their mechanical properties and it is well known that the coercive force and yield strength have strong correlation. We have developed the in-line method to measure the magnetic properties correspond to the coercive force. The measuring system has a set of magnetizing magnets which are assembled on both side of steel sheet and the constant current are applied to the induction coils of each magnets. The coercive force is calculated from the hysteresis curve obtained from the magnetizing current and the magnetic flux measured by the search coils. After clarifying the effects of several disturbance factors the in-line measuring system was developed and the results for several products were achieved. The coercive force measured by our system had good correlation with the yield strength measured by the mechanical test. In this paper, the principle of measurement, the specification of the measuring system and the results of in-line test are proposed.

Modern medical prosthesis includes a wide range of bioactive composites glasses, glass-ceramics and ceramic-polymers. Biocompatibility properties and resistance to mechanical stress represent the most important features when designing new materials based on ceramics for medical implants. Zirconium oxide doped with rare earth elements is an important candidate material for incorporation in medical implants and prosthetics. Due to their mechanical properties, the doped compounds hold a unique place among the oxide ceramics since they can go through phase transformations allowing a toughening mechanism. The substitution of the Zr atoms with Y or Ce allow the obtaining of ZrO2 based materials resistant to structural changes at room temperature and resist crystallographic transformations from tetragonal to monoclinic, subject to high mechanical stress. In this study we aim to investigate the phase stability of ZrO2 ceramics following Y doping. Two types of samples have been investigated, namely polycrystalline samples obtained by means of ceramic technologies and nanopowders, both doped with Y and submitted to thermal treatment. Combining characterization techniques based on XRD, ND as well as Scanning Electron Microscopy with non-destructive evaluation methods, we emphasize a unique approach on evaluating the physical properties of these ceramics.

Visible Reflectance Spectroscopy for The Characterization of Glass in Historic Objects

Presenting author(s):
Dr Christina Bisulca

Co-Authors: Mr Mattie Dugan

Room: Mediterranean | 2:45 PM Thursday, September 19, 2019

Fiber optics reflectance spectroscopy (FORS) is widely used in cultural heritage for the analysis of pigments and dyes. In this study, we assessed the utility of this technique to characterize the colorants in historic glasses. Reference glass samples were characterized with both x-ray fluorescence spectroscopy (XRF) and FORS to identify the colorants. Using this technique, the glass was characterized in a wide variety of artifacts including glass beads, enamels and glazed ceramics. There are several colorants that have characteristic absorbance patterns in FORS. While FORS spectra are more difficult to interpret, FORS equipment in the visible is much less costly than XRF equipment. Moreover, FORS is very sensitive and can identify colorants even at very low concentrations. These results show that FORS for the non-invasive characterization of glass warrants further research.

About the Possibility of Magnetoacoustic Spectroscopy of Ferromagnetic Materials

Presenting author(s):
Mr Evgeny Serbin

Co-Authors: Mr Vladimir Kostin

Room: Mediterranean | 3:10 PM Thursday, September 19, 2019

The magnetoacoustic emission (MAE), i.e. the whole set of elastic vibrations arising in ferromagnets upon their remagnetizing is extremely sensitive to the features of the structural-phase and stress-strain states of materials. Under low-frequency excitation, the main mechanisms of MAE can be considered local excitations of elastic vibrations by an irreversible displacement of 90-degree domain boundaries and the resulting size change – magnetostriction.
The use of the averaged value of the flow envelope of elastic vibrations does not allow to selectively evaluate the contributions of various mechanisms of the formation of MAE and determine their relationship with the structure of materials. In this work, the spectrum of magnetoacoustic emission in iron-based alloys was studied using broadband acoustic emission sensors and digital spectral signal processing.
The effect of the excitation and detection conditions on the parameters of the magnetoacoustic emission of ferromagnets of different chemical composition is investigated. The non-monotonic nature of the frequency dependence of the MAE amplitude for a large group of ferromagnets of various sizes and shapes has been determined.
It is revealed that with increasing degree of plastic deformation of 30CrMnSiA steel, the amplitude of the spectral components of magnetoacoustic emission decreases more than 10 times. Based on the analysis of the spectra, it can be concluded that the maximum amplitude of the MAE spectrum shifts to a higher frequency range with an increase in the degree of plastic deformation of 30CrMnSiA steel.
The previously established presence of a correlation between the amplitude of the magnetoacoustic emission of annealed steels, the field corresponding to the maximum MAE, and the residual magnetic induction allows us to recommend these parameters as structural-sensitive testing parameters. In this case, it is possible to contactless register elastic vibrations by scanning systems of materials characterization using electromagnetic-acoustic or optical transducers.

Program coming soon

Exhibiting at the Symposium

A limited number of table top exhibits are available. If you are interested in having a table top exhibit to share your latest products, technology or service offerings, contact Ruth Staat at rstaat@asnt.org or call her at 614-274-6003, ext. 227.

About Portoroz

Backed by an idyllic countryside of the Slovenian Istria and flanked by a lively sport marina, Portorož is a Slovenian Adriatic seaside resort and spa town located in southwestern Slovenia. Its spas offer therapeutic treatments based on the mud and brine from the nearby Sečovlje Salina salt pans. The central Portorož Beach is a wide, sandy stretch with wooden piers. The hilltop Church of St. Bernardin is a former monastery from the 15th century. To the south, Seča Park is home to Forma Viva, an area dotted with stone sculptures.

Hotel Information

GRAND HOTEL BERNARDIN 5 *****
(Symposium will take place in the Conference Center at this hotel)
150,00 EUR per night (180,00 Double Occupancy)Click here to make a reservation at the Bernardin

The hotel recommends GoOpti for a low-cost shuttle company to reach Portorož. They offer transports from all the airports mentioned above, as well as many train and bus stations, and even custom locations, to the Grand Hotel Bernardin.

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Committee

Organized by The American Society for Nondestructive TestingHosted by The Slovenian Society for Nondestructive Testing